I typically get 3-5 years from car batteries. In every car I have owned (there have been over 30 now to date) this has been the case. Usually they tend to give some warning, but sometimes just work one day and are dead the next.

The wierdest battery death to date, ironically, just happened this past Sunday to my wife and I on the first road trip we took in the new-to-us 1994 850t wagon. We were in Palm Springs (around 400 miles from home) and were out driving around and stopped off at a store. When we came out and tried to start the car--nothing, battery completly dead. Thankfully a gas station was right across the street with an open service department to come to a quick (but spendy) rescue.

I do have a question though. I normally don't carry much more than a AAA+ card when travelling, despite being someone who does their own maintenance. So, a volt meter was something I did not have (to verify the charging system was okay). In my Audi I can go into a diagnostic mode on the automatic climate control, scroll to screen 11, and view a nice digital readout of the car's operating voltage. Is there such a hidden feature in the 850t??? Just curious.