I don't bother trimming until it measures past 1.755 just to make sure it has room to expand but since its semi it shouldn't be an issue. Dont make more work for yourself than is necessary. Trust me it gets old after a while, be safe... yes, but over diligence can burn you out too.
As far as accuracy, having different cases lengths isnt going to be a bother to accuracy as long as your are measuring per O-give anyway. Yes you'll have to adjust a bit on the seater die but that's necessary anyway if your working for accuracy.