Noticed a slow crank while starting the X5 Saturday morning so I check my receipt on the Autozone Duralast battery I installed - June of 2008! So I hurried on down to Autozone for another H8. Only about $20 more than the one it replaced. 91 months of service is the longest I've ever had a battery go in anything. No doubt keeping them away from the engine heat contributes to longer life.

2002 X5 3.0 294,475 miles
2014 428i 15,000 miles

2004 325i sold at 123,600 miles
2001 325i sold at 66,000 miles