I have 10 mags for my CZ SP-01, but it seams like I am always using the same one, my number 5 (all my magazines are numbered).
I could safely say that #5 has at least 5000 rounds through it. Still going strong, and for what it's worth, I never keep them loaded. I manually load as I shoot, it gives me time to reflect on my last 15 shots while I reload my magazine for the next training round, and I always load 15 rounds in them, just a habit.