I keep 70 - 80 1911 magazines.
I buy the least expensive I can find ($10 - $12).
I test each in ALL my 1911's and discard those that don't function flawlessly in all of them.
If one stops working, it goes in the trash. If one gets gummed up with sand or mud, it goes in the trash ( life's too short to fuss cleaning up a muddy $10 magazine).
Magazines are fungible and not made to last your lifetime, although many of mine have seen 20 - 30 years of service.
I don't baby them. I drop them from the pistol to the ground, without worrying about what they land on (can you imagine how silly it would be to slow down to protect an ejected magazine in a sd situation?).
For pistols other than 1911's, four or five magazines are plenty for me.
Of course , I don't use those pistols for sd or competition ( other than some of my 22's).
How many magazines you need depends on what you do with your pistol. For those who occasionally shoot a pistol, 4 or 5 magazines will do.
If you're doing serious shooting, you need lots more.
Just my opinion, of course.