I just replaced the crap Napa battery in my MV, four years in, only 30K miles.
Driven regularly, but not daily. Started to crank slow last fall, charged it,
and seemed fine until I came back from two months away in my big camper. The MV
was in the garage all that time, not heated but never below freezing, and was
completely dead when I returned, < 6V. No external draws. I replaced it with an
Odyssey AGM battery.