One big advantage of playing in a one hour playing session is that it is much easier to come out a winner. Weather if you have a positive or negative expectation when you play you are more likely to come out a winner after playing for just one hour as oppossed to 4. If you are playing with an advantage if you only play for 1 hour it is likely that the casino will see your winnings as "luck" rather than skill.
Another advantage of playing a 1 hour session is that you will not get fituged and will make less errors.
One note on this is your playing session does not have to be an hour exactly just some where in the neighborhood of an hour. I prefer to cash out my chips in the middle of the deck when the count has gone south rather than at the start of the deck. If you always end the day when the count has gone south you can increase the amount that you win because the next time that you come back the deck will have been shuffled and all the cards you want will become available again.