Eh. I keep 90 odd AR mags laying around loaded. Good way to store ammo. Only about 16 of my mags are P mags. I keep an extra 1000rds of M855 on strippers with some spoons tossed in a can next to my pile of mags. Eh. Better safe than sorry.

Anyway, some apparently knowledgeable folks, such as Larry Vickers, say to load your mags only when you need them. There is some information to suggest that USGI type alum. 30 rd mags might have issued with feed lip deformation if left loaded a really long time. I haven't had it happen mind you, but something to consider.

P mags are nice, but I wouldn't get rid of all my other mags just to use them. All eggs in one basket being a bad thing, yada yada.

I also simply keep an M7 bayonet (cheap, stabby bayonet goodness) fixed on all my M4 clones and my Colt A2 semi. All else fails.... I've got that.

You probably want a min. of 14 to 20 loaded mags ready per rifle. Whatever your max combat load is that you're comfy hoofing it with.