When I was in the service, I did a bunch of training and shot a lot of rounds downrange.
Once, during a trench-clearing live-fire, we were shooting so much, so rapidly (1) folks' hand guards were melting, rounds would cook off in the chamber, and we had one chamber blow out.
We started off each iteration with, minimum, 210 rounds apiece and most packed more. It got shot up right quick. There were several iterations during the day & night. PM, water, reloading mags between iterations.
I was one of those who carried more than 210 rounds, as I had access to more magazines and didn't mind the weight so much.
These days, I doubt I'll clear trenches with anything but a spade. 210 rounds is not "a good start" but a number of rounds completely out of the realm of reasonable.
Compromise is a reality check.
I think this is where 320's comment comes in.
Any CCW is a compromise.
If I had my druthers, I'd pack a shotgun & slugs or a self-loading rifle.
30+ round mags against some of my old buddies in armor toting M4A1s, SAWs, M240Bs, Gustavs, (all with a full combat load of ammo) & such would not be much more useful than a 1911 and a spare mag or any other CCW you can think of.
When it comes to CCW, we compromise functionality for concealability. Some want to pack more mass/gear in case they face multiple attackers. I, too, sometimes pack more gear/weight, but more as failure mitigation. The extra mag is if the mag in the weapon is faulty. My ankle or pocket-carry CCW is if my primary doesn't work for some reason.
I did, however, just get a new double mag-holder, so my on-board ammo for my SW1911 will bump from 17 (or 19 if I use my 10-rnd Wilson) to 25 (or 29 if I pack 2 spare 10-rnd Wilsons).
(1) M4A1 & other heavier-bbl M16 variants rated at something like 12-15 rounds/minute in sustained fire