I still have the original battery in my E Class Estate, May 10th 2009! So only 14 years! Today they re-gassed the air conditioner, only just stopped working & I didn’t know it worked on gas until my husband was discussing checking the gas in the combine before harvest! Such a surprise, no wonder it stopped working after 14 years…the garage was most amused…and surprised!I changed my E class battery at 15 years. It was still starting the car just fine but I chickened out and used the battery that came out of my r129 (I tested it with my battery tester and it was deemed good).
In my experience same make type as replacement never lasts same as origional???????? But 10£ a Yr for 10yr ain't bad battery cost and in France u will get 6 euro for Yr old one!!Just been through the same decision with my CLK and its 10 year old battery , it was showing 12.1v at start up and seemed to be taking an extra turn to start up .
Decided that as MB's hate low voltage , and modern batteries sometimes just fail without warning . I decided to get a new one from MB Grangemouth (with forum discount and delivery £110) Paid £130 for my E class battery from Grangemouth last year .