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

[Boobie Lover]

It is something I've been thinking about. Recently, I've been playing longer sessions, and some situations have arisen in which I have the potential to play 200BBs pots against players that I think are inferior to me. So, do you think that your potential winrate can be affected how long you can play a session effectively? Like say if a person were a 4 ptbb/100 winner if he usually plays 2 hour sessions, that if he could play 4+ hour sessions at the same or slightly lower level that he could become a 6 ptbb/100?

Of course, if you haven't figured out yet, I'm talking about max buy-in big bet games.