As others have said, games do tend to be softer in the weekends for fairly obvious reasons. Less people working = more recreational players having time to play poker. This is on an "everything else equal" basis though. 2NL cash games played at the worst time will still be softer than 25NL cash games played at the best time. But if you are trying to move up and take shots, it makes a whole lot of sense to do it, when games are best.