How much is winrate affected by how long a session you can play?

[ashmc2]

I think that my win rate goes up the longer I play. I play more aggressive early on and am willing to go a little further on drawy boards. This is just me. I'm a little hi-strung and it takes me a bit to mellow out. Win I play for a few hrs I get in a zone and make smarter calls and plays. even multi-tabling. You can do that in short sessions; at least I can't.