Duration and Frequency
Running a game is a lot like holding a class. There are a lot of benefits to longer games, if you can manage it.
The first half hour is people arriving and getting set up (gamers are often late). The next half hour is recap of last game. Longer games require breaks just like longer classes.
Time between games matters more if complex situations are split across multiple games. That is, if you can wrap up the action and resolve the hook by the end of the evening, you can wait a lot longer before your next game session without the delay causing problems.
Shorter game sessions make it harder to resolve a plot hook before the end of the session. So you need to play more regularly.
Let's look at some examples:
Let's say your starts at 7:30pm, ends at 10:30pm (3 hours) and runes every other Monday after work. One scene is one hour (including the scene transition). With the arrival, setup, and recap of the last game, you will have 52 scenes a year, assuming you never miss a game. (52 weeks, 26 games on an every-other-week schedule, 2 hours of actual play per game, 26*2=52)
Let's say your starts at 10:00am on Saturday and ends at 10:00pm (12 hours) with 30 minutes for lunch and 90 minutes for dinner (10 hour game) and runs every other month. One scene is one hour (including the scene transition). With the arrival, setup, and recap of the last game, you will have 54 scenes a year, assuming you never miss a game. (12 months, one game every two months, 9 scenes per game, 6*9=54)
Gaming is a hobby, and people have a hard time prioritizing it over work, dating, childcare, family, or even other hobbies. For working adults, workday nights can be the best time to play, to avoid their busy social lives. Parents with children either have to get their partner to cover childcare, get a babysitter, or have game at their house after the kids go to bed; but a short game is easier to manage in that case than a long game unless it's infrequent.
I recommend scheduling games either regularly (every other Monday), by consensus (using something like Doodle), or with at least 60 days advance notice
You need a plan for handling absent players, unless you're using consensus scheduling. Common options:
- Someone else plays the missing player's character
- Game is cancelled if someone is missing, or you play board games or watch a movie
- The missing player's character "fades into the background" except for any plot-relevant items or information he may have.
- The GM plays the missing player's character (generally similar to fading into the background except for group challenges and combat).
Often at the climax of major plots, the GM is going to want everyone to be there for the game anyway.
Telepresence is another route you can take to getting people to your game table. An iPad or webcam-enabled laptop (or full telepresence unit, for lucky rich gamers!) will allow players to attend the game virtually. If you have enough cameras around (say three people have iPads and two have laptops) you can have cameras watching the GM, the other players, and the battlemat and minis (for that sort of game). In that case, I recommend google+ hangout. The remote players can switch between views, it's available on PC, Mac, Android and iOS, and, more importantly it's free and reliable.