The CYA is only going to drop by backwashing or by splashout, so it's possible for it to fall some during the swim season, but not likely by very much. Ben is by far the most knowledgeable one here, and I'm guessing he has a reason for not draining/refilling to get the CYA under better control, and would defer to him, but just wanted to add my opinion here that it certainly won't hurt to drain/refill some of your water, and personally, if it were my pool and could do so without much of a problem, I would go ahead, unless the levels of other chems in your fill water would substantially change the current levels in your pool.

Janet