I have 4, and an md20 on order. I think that is enough. Sure, more of something that is hard to get is good, but do you really need more?
Could you spend the "more mag money" on other, more practical things, like, say, a new Glock or something instead? You live in CA so that seems unlikely, but who knows.
I have 13 Pmags for my AR15s. I wish I bought more of those, when they were readily available for $13 a pop with the chrome silicon spring. Still, truth be told, if the zombies are coming, an S12 with an md20 loaded, and 4 AGP 10 rounders in reserve along side a couple ARs with 1