I'm guilty of not having any "spare" magazine. I got three for my glock, three for my FNS and two for my wife's XD. I need to buy some more but haven't yet. My eventual goal is to buy two more for each pistol. I figure though that with the compact pistols I will buy the full size service magazines and buy a new spare springs for the flush fitting magazines as I don't want to spend the money on a spare 12 rounder when I can get a 17 round magazine. The spring is what takes most the wear and maybe a follower wouldn't be a bad idea. Those FNH magazine are pricey! Like $50 a piece!
My rifles are pretty we set with the AR15 having 10 and the M1A having eight. I know one day I will regret my neglect of my fully loaded pistol mags and start having failures. I need to get on it and just invest.