Mathew and Attila discuss the ideal length of a gaming session. Games discussed in the show:
Play Session Basics
Session length refers to the amount of time which a player spends in a game from the moment they turn it on to the moment they turn it off. From lengthy MMO raids to a few seconds spent playing a mobile game between stops in public transit, you must divide your game into session lengths that best accommodate the intended audience. Sessions can be thought of like chapters in a book; natural divisions of a game experience between which the user can end their game session or continue as they see fit.
One simple way this division is achieved is to break your game up into levels, but this isn't always possible given the nature of the game. Otherwise, a save / load system of some sort must be implemented which can allow players to dictate their own session lengths. Of course, with the ability to save and load anywhere comes the potential for abusing such a system to artificially deflate game difficulty. However, not every type of challenge is prone to abuse from "save-scuming" and the issue can be circumvented by only offering a "Save and Quit" option to the player. This way, the creation of the save file allows players to jump out of the game whenever they need to, but doesn't allow players to save and keep playing, reloading the file whenever they fail. Another approach is to limit saving / loading to preset save / load points; physical places in the game where the player must interact with a game entity to save their progress. This still allows you to dictate what transpires within a play session, although it is not as accommodating of length. Perhaps the ideal solution would be a combination of Save Points and the ability to Save and Quit from anywhere, as this can allow players to drop-in and out of a game at will while preserving the intended challenge of the game based on the location and scarcity of save / load points.
Getting into the Game
If it takes 5 minutes to get past the opening logos, loading the title screen, and then loading the save file, players probably won't feel like even opening the game unless they know for certain that they can commit to a longer play session. When I designed the main menu for Zarnok Fortress, I made it so that the main menu appears instantly without any splash-screens to get in the way of the game beginning. I also ditched the idea of the "title screen" which does nothing but display the name of the game and a message that says "Press Start to begin". The "main menu" is the first thing the player sees with the cursor positioned over the one-click-Continue button that instantly loads the last-played file. This means from when the user launches the game, they can start playing instantly. If you're intent on having splash-screens display before the game begins, I would suggest only having them appear the very first time, or at most the first few times the game begins. Beyond that, the logos can be featured on the Main Menu screen if you're really intent on reminding the user who it was that made the game they are playing. In the case of Zarnok Fortress, I further gave players the option of selecting how the game would load the levels. By default, the game loads levels one at a time since this has the least amount of up-front time cost. If a player is in for a longer play session though, they can elect to have every level pre-loaded into memory to speed up the time between levels, although this makes them sit through a long load before they can get into the game. I know just enough about asset loading in games to understand that offering this kind of choice isn't always possible, and may be severely limited by the amount of memory available from the game hardware, but when you can offer players this choice, they are sure to appreciate it.
Getting BACK into the Game
It can be tempting to enforce control over the length of a play session by not letting players quit out of the experience in the middle of something important, like a puzzle to which they might forget the details. If you've ever stopped playing a game for any length of time only to return to it utterly bewildered about what you should be doing or even what the controls are, it can kill the experience and make a player drop the game for good.
In defense of Fi from The Legend of Zelda: Skyward Sword (you'll never hear anyone else say that) she could at least remind you of your current objective, as well as give hints on how to get there. This is useful not only for players who are stuck in the game, but also for anyone resuming a play-through from an extended absence. Another, more elaborate solution from Pokemon FireRed / LeafGreen was a Journal that kept a log of everything the player had done recently, playing it back to them at the start of their next play session. While this system didn't give you a hint as to what to do next, it did contextualize everything you'd done up to where you left off in the game, which might have been enough to jog your memory into remembering what you meant to do before concluding your previous session.
One thing I haven't seen done very often (but something I believe would be incredibly useful) would be the ability for a player to access a quick primer on the game's controls to remind them of what does what. This is more important for games with a large number of different inputs, or games like First Person Shooters which can have small differences in controls from game to game. It would certainly be useful to a player coming fresh off of a session in a different game where "Right Bumper" performs the reload action, where now they need to press "X" instead.
Session Length by Platform
The length of individual play sessions must be influenced by the platform the game is being played on. Platforms can be broken down into a few distinct categories (in truth it's more of a sliding scale based on device capability and usage): Mobile, Handheld, and Console / PC. Of course, the platform a game is played on is not the only factor in session length, as more powerful devices can play host to games with session length structures of less powerful devices, and modern smartphone devices are capable of rendering experiences akin to full Desktop experiences of just a few years ago, so the following is mostly just a helpful generalization.
Mobile refers to games played on a Smartphone (typically with only one hand, as the other is likely occupied holding onto the safety bars of whatever transit system the player is riding). These games should have the absolute shortest possible session length, as little as the amount of time it takes to get between stops on a subway (under one minute). These are the kinds of games where Iteration Time becomes incredibly important; how quickly can a player retry a challenge which they have failed at? When I designed the parody game Cliff, I made it so that the user doesn't even need to touch the screen when they die, they immediately restart the game and continue from where they left off. This can shave down precious seconds which are actually large fractions of time when dealing with sessions this short.
While the handheld market is being carried almost solely by Nintendo's 3DS, and may not be much longer for this world in its current form, it serves as an important middle-ground in the sliding scale of session length. Anyone who packs a handheld game system in addition to the smartphone they probably have is likely in for a long trip, or is a dedicated gamer. Handheld games must play host to a wide range of expected session length that bridges the spectrum from Mobile to Console / PC. As such, it's difficult to put numbers to the exact session length because it depends so much on the kind of game being played, but lets say it occupies the range above 1 minute up to around 15.
Console / PC
These are the heavy hitters; the games which some players actively schedule around so that they can continue to enjoy them even as the amount of free time in their lives dwindles. These are games which can convey stories of massive scope (made by Indie and AAA alike) or multiplayer matches which have a minimum session length of 15 minutes (bear in mind that the time limit on causing eye-strain is 20 minutes of up-close focus). While games of this scale can tempt a player to play from beginning to end, it is the responsibility of the designer to build in break points at the upper limit of 40 minutes. At this point, give players the chance to come up for air, even if they decide to simply dive back down into the game. If you structure your play sessions to be much longer than this, players may not be able to finish your game because they cannot invest the necessary time into a single play session.