Position position position.
I wouldn´t try to rep trips UTG. Also of course consider the number of players still in the pot and their pot commitment. More players means both greater risk that someone has trips, AND you´ll get a harder time getting everybody to fold.

My experience is that if the board pairs, and the pair is medium or above, and there are still some people in - at least one of them has a strong hand that he is willing to call all the way with.