I don't use permethrin, but know of a peach grower in the area that alternates permithrin (Pounce) and Imidan in his summer spray program. Claims he gets excellent results.

If you are seeing "strikes" the day after you spray, it's likely the eggs had already hatched into larva and penetrated into tissues before you sprayed, thus protected from your spray.

Once eggs are laid, it takes 5-21 days for them to hatch (depending on temps). Permethrin is supposed to kill eggs on contact, but not larva that have already tunneled in fruit or shoots.

I don't know how often you spray, but if not that often, tightening your spray interval might help.