Federal regulations says they must last 80K miles, most cars are warrantied to 100k or longer. There are teslas on the road with over 200k miles or more on their original batteries. 400k on prius taxies and ubers.

How far does a postal delivery van go in a day 20 miles, 30 miles ? A small 35KW battery could do double that, in 10 years if it's lost 15% capacity it could still do it.