At anything less than the $50 NL tables I'm not willing to fold TP/TK on a board with no straights or flushes possible. At the higher tables you won't find many players paying you off with just TP so if they are coming along it usually means you are beat. But in my opinion at the lower limit tables the ratio of players who will pay with their stack with just TP overcomes the losses you will incur when you get hit by a set or two random pair.