Hiya: I think the best time to play has NOTHING to do with the Casino, and EVERYTHING to do with you. You should only play when you are, Happy, in a good mood, content, relaxed, and so on. If these things happen to corespond to a certain day, or certain time of the day, then this is when you should be playing.
Why? Because if you are in a good mood, ect, and getting your butt kicked, it is a lot easier to say, "Wow, this game is kicking my ass", and to simply log out, and go back later.
vs
Playing when mad, or upset, or under stress, ect, and getting your butt kicked, and saying, "Yea, this game is kicking my ass", and thinking, so what else is new, i don't care, and end up just continuing to hit that Bet button.