The phrase "lot of miles" means a large amount or distance traveled. It is an idiomatic expression that refers to a significant amount of travel or movement.
Sentences with «lot of miles»
I have lots of miles on this car and it still works really great. (autolist.com)
You're going to be dealing with that for a while; you've got lots of miles left to go. (bonappetit.com)
You want all that on a car being driven lots of miles. (extremetech.com)