Mine had to be replaced within a few months of us buying the Bounder. When I checked the dates on the ones I took out they were a year older than the build date of the coach. So indeed they were about 7 years old. The starting batteries failed even sooner.
Mineral oil? I'm interested.
What kind of mineral oil did you use and where did you get it? I've read quite a few posts that say not to use drugstore oil, other that say it's fine, others that say mineral oil will make your batteries last forever, and some that say it will ruin them. Who you gonna believe?
I don't mind adding water. But the corrosion is starting to just plain piss me off! I have to scrape it off and spray with battery protector much more often than I think reasonable. The new battery retainer clips I coated with plastic are already starting to fall apart, and the little suckers were not easy to find!