RV anti-freeze doesn't "spoil" any more than water would. It's a stable product, propylene glycol, that doesn't change chemically just sitting in a closed container, and is also used as a food additive. If it's not contaminated, it's good pretty much forever. When it's on sale I stock up, and I'm using stuff that is years old. One spring WalMart was clearing out their RV anti-freeze for $1.00 a gallon. I bought a bunch.
curmudgeon: noun; a crusty, ill-tempered, irascible, cantankerous old person . . . .
79 27' Holiday Rambler Statesman, 78 32' HR Imperial, 85 36' HR Imperial 5th Wheel