Originally Posted by awns729
I wantto say i remember reading in the manual, that the battery isn't supposed to need replacement for an extremely long time, especially in warm climates. Worth looking it up in the manual if you're curious.
I looked it up and the online '08 manual (with iDrive) says on p. 220 that the electrolyte will last the life of the battery. It says nothing about how long that battery life will be.
Average BMW battery life seems to be around 5 years, but YMMV!