This is quite amusing. Unless the battery has some cliff where it stops working (very unlikely) my anecdotal experience is that the battery has a very slow degradation rate (2-3% over 5 years - great considering I have a 75mi roundtrip commute).

On the other hand, I don't pay for: oil/fluid changes, filter replacements, transmission/engine rebuilds or smog checks. Probably forgetting a half dozen other things too.

Add all that up and it's a free battery replacement in 10 years which I don't even think I'll need.