2020levo SL expert 4000 miles!

I just bought this bike from a 76 year old guy who had it since new. It is in like new condition and everything works. I had it gone over by my local bike shop and they said it had 4000 miles on it! How many miles are these motors good for? It does have some upgraded parts, new cassette, brakes etc. but I’m assuming the motor is original because the owner didn’t tell me otherwise.