Spare Parts for AR 15's. What Do You Keep Around?

I'm concerned after elections next year the gun grabbers are going to be hard at it. I think they are using California and New York as test areas right now. Hopefully I'm wrong, but, I want to be prepared. I have a couple AR's and have purchased an LPK from PSA. Thinking of getting another LPK and I want to get a 1:7 upper from PSA when funds are available so I can push heavier rounds down range. Since I've never had any problems with either of my AR's, I'm curious as to what people keep around for spare parts just in case. I hope the gun grabbers don't gain any traction next year but if they do, I'm concerned that evil black rifles will be at the top of the list. Wondering what parts people see wear out or break the fastest. I want to be able to keep my rifles functioning for years to come, even if parts become available. Hopefully those in power will respect the 2A, but you never know.