I see reports of Tesla Model S early adopters in the USA selling cars that are now 9 years old and with 250,000 miles run with only a 10% loss of battery efficiency.
Battery life can be shortened by careless use and charging, but overall I get the feeling that Tesla have a good grasp of battery management and so can promise a long life.

Peter,
66, 2016 Porsche Boxster S
No longer driving Tarka, the 2014 Plus 8...