by spoon http://www.flopturnriver.com/pokerfo...st-151254.html
If you want to be able to play long sessions with any frequency, your first priority is to be aware of how long you can go before you start getting burnt out. By burnt out, I mean you start playing worse because you really don't care anymore and you want to get up and do something else. For example, if you work a 9-5 and usually play for an hour and a half in the evenings three or four days a week, your threshold is probably around 2-2.5 hours four times a week.
So here's what you do. Start off by paying attention to how long you're normally playing each session, each week. Hell, write it down or keep a text file that lists how much you play and each day for two weeks. Don't do anything out of the ordinary, just keep up with when you play. After you know where you're at, you want to try to start adding 15 minutes to the end of each session for a couple of weeks. If you play four sessions a week, this is going to give you an extra hour of play without taking up much time on any individual day.
The idea is to start conditioning your mind to handle poker information for longer and longer times, but if you don't focus on your whole session, including the extra 15 minutes, then you're basically wasting your time and will gain very little from this process. To make the most of this extra 15 minutes, make sure that when that 15 minute block comes around that you're actively engaged and trying really hard to stay focused on the game. You won't improve your playing stamina if you slack off and half-ass through this extra block of time. Now take a couple of weeks and focus on maintaining concentration through your whole session with this extra 15 minutes added on. Once you get in the habit of staying fairly focused on what you're doing, add another 15 minutes to each session and continue the process.
It sounds pretty simple because it is, as long as you don't get ahead of yourself. If you start in your comfort zone and incrementally increase your playing time to whatever goal you have for yourself, then you'll achieve your goal with relatively few growing pains. The people who have the most trouble learning to play long sessions tend to try to jump right into playing eight hour sessions six times a week when they're used to playing two hour sessions four or five times a week. Your mind cannot adapt to that big of a change so quickly and maintain (or increase) the level at which you play the game. If you try to play this long of a session out of nowhere, you'll start playing horribly at one point or another -- look at any thread where someone has played a 24 hour session (who wasn't used to it) for proof of this.