I was going to put the one in from my pickup but that's only 470 CCA and my tractor OEM is 570. It's the only one that I use, so not like I'm to maintain several the way that you are.I only put new batts in tractors that I absolutely have to get going when I get on it, after that, they get "hand me downs", and in the cold, I put a batt. tender on them.
With a tender, they take off like new, and once started the tractor starts easily the rest of the day.
SR