I don't see a difference between a well-patched tube and a new one. One spare [whatever] tube and a new-within-a-couple-years patch kit works for me.

I guess I average about a flat per month. It's rare I have problems the above combination can't handle. Occasionally I'll have to make a call of shame, normally because I didn't notice I'd worn out a tire. Caught heck last year on my second call of shame in a year; I'll have to do better checking the tires.

FWIW, last big can of Rema fluid I bought from Amazon arrived half dried out. I've been using a can of Slime from the auto parts store for the last 4-5 years and haven't seen any change in how well it holds the patches.