Mine went 6 yrs, and I suspect I could have pushed it further,
but I wanted to replace it under "my time" in the driveway, not
dead on the highway somewhere.
There are several brands available that are direct replacements
in lieu of the stlr's $200+ batt.
Easy DIY: maybe half an hour. See my thread link and also
note another link at bottom of verbage, above the pic series.
GL, mD
Battery R&R:
http://www.xoutpost.com/x5-e53-forum/...apped-out.html