IMHO carrying 2 spare mags gives me flexability to deal with whatever may come should it ever be needed. I have one loaded clip of gold dots and a spare of gold dots and then maybe some corbon or another premium round.
This last clip I look for rounds that have a somewhat greater penetration than even the gold dots and yet a still a JHP, just in case...
Would I ever carry more clips? Sure but there would have to be a good reason to do it like zombie hordes or some really serious situation that for whatever reason I had to endure or venture into. I just don't see it happening but who knows may one day I might find a reason... Certainly I wouldnt seek out such a thing.