It varies for me, I can spend 3-4 hours on a game and I can spend 10-12 hours. My longest session lasted 12 hours. I play mostly cash games, so I can interrupt my session at any time, go do some other things, and then continue playing again. If I play tournaments, then a maximum of 3-4 per day, maybe a little more, so that I can enjoy and get high from the game. If I treated poker as a job, I would most likely play at least 8 hours a day, but now poker is a hobby for me.