I have a 9mm CZ75, purchased it used, but it could have passed for NIB. Anyway over the last year I've shot maybe 1000-1500 rounds through it, almost all White Box. It seems that the last few range trips it has had snappier recoil. For a while I thought that Winchester had changed their ammo, but that would seem less likely than recoil spring wearing. Thoughts?

One prime indicator of recoil spring wear is how the pistol ejects spent cartridges. Most pistols eject farther and with more force as the spring weakens. Many CZs tend to throw brass a goodly distance even when operating normally, but if you are throwing the brass farther than it used to it's a good indicator that a spring replacement is in the cards.

Or, you can order a replacement spring now, and wait to replace it when your pistol actually starts malfunctioning.

Springs are cheap, order 4-5 and keep spares in the safe.