I replaced my two original equipment Interstate Workhorse 6V in 2012 at 14 years plus. Honest folks, FOURTEEN PLUS! As of now, I'm still using the Sam's Club Duracell's that replaced them. I think the key has been keeping them on a smart charger full time and checking the electrolyte level regularly. I only fill when needed with distilled water only. I'll admit that we don't boondock much and use the generator liberally when we do.