How long would you expect a battery to last?

[Sirrel Squirrel]

Just got my 2005 E350 back from the garage as the EML light came on and was reporting lots of undervolting errors.

Turns out the car has never had a new battery and the one that was in there was from 2004!

 

[Sirrel Squirrel]

O yea I was amazed it was still going as I thought they only lasted around 5 years.