The lead battery life expectance is 5 years.
May last longer. I change my battery on 190D after 7 years.
I don’t know if the battery which you have is maintenance free or you can check the acid by hydro miter. Each cell has to be in same level.Normally one of the cell getting short by the lead.
On my 260E battery last only two years.
4.5 years is very good.

Best Regards.