Simple question, but when was the last time you check the levels in each cell of the battery? Do it quickly if you never have before...
The original battery on my '99 Boxster lasted 10 years almost exactly to the day (b/c I'm not sure which day in 10/98 it was built
). Only during winter storage did I need to put it on a maintainer. Checked the level of it before putting away for 4-5 months, once again when taken out of hibernation, and mid-season: July-ish.
Top off the cells w/ distilled water as needed.
FWIW, after the OEM finally kicked, I replaced it w/ an Optima Red Top for more of a true maintenance free.
