It depends on how much you want to dial in the model. Ideally a model should not need to be retrimmed, but I find that any given day I need to give a control a click of trim one way or the other long after the model is "trimmed."

That may be due to the way I'm seeing the model on that day or who knows what. It could be that climate plays a part too in that the structure may change slightly.

A lot of guys swear that nyrods change length with temperature, but I haven't noticed that models of mine using nyrods need any more or less trim than models having pull-pull controls, carbon fiber pushrods or anything else.