Bought new 2-28-04, purchased batteries: 9-25-06 and 7-18-08. No leakages found by dealer. What’s wrong? Actual mileage slightly over 31,000.
You drive mostly short trips, right? Lots of starts, not much charge time (I would guess).
A trickle charger (solar or otherwise) will help maintain your battery charge for longer life.
Possibly try a better grade of battery/different brand?