It depends on when I put the last new ball in play. If I put it in play half way through the previous round I probably start the next round with it. I won't go more than 36 holes with a ball and that is pretty rare. We have coquina/sand cart paths (no drops) that don't really mar a golf ball. Trees will discolor a ball but most of my damage comes from bladed bunker shots. Occasionally I will lose a ball in a water hazard, whoops, penalty area. Also, we have an older tree with an opening in the base that is just right of the 18th green. Many times I will toss my ball in that opening to pay homage to the golf trolls/tree monkeys in hopes that I will get favorable bounces my next round. "I'm not superstitious but I am a little stitious."