The first thing you need to do is atleast use some common sense. Nobody is going to argue that its clear what a 'session' is but its obviously not a month or a year. Is it a day? Probably not but maybe the IRS won't bend you over if it appears you are trying to be cooperative.
But the important thing here really isn't what you or I think a session may be. It's what the IRS will think. If you get audited there is no way they are going to let your 'year session' theory work. They will find that you owe more taxes. They will find that you owe interest. They will penalize you. Now what do you do? Fight it? You can try but you have two problems. 1) You will have a hard time winning as it appears you didn't even try to comply with the law and 2) even if somehow you win your attorny fees will at a minimum be sevearl thousand dollars.
Here is a link to an article by Russ Fox (a CPA, poker player, and 2+2er) which may help with figuring out what a session is...
http://www.gambling-law-us.com/Artic...ng-Session.htm