Older thread, but this jives with what I've seen/heard/read in other threads on FT and in my experiences within the industry:

Alamo: Unlimited Mileage Cap?

And typically, exceeding those soft limits slightly one time isn't going to do anything. The issue is mostly constrained to serial abusers who repeatedly drive >3,000 miles a month for multiple months in a row.

I was in rental cars with Hertz pretty much solidly from about 1/20 through 3/5 and probably put on a combined 4,000 miles split across 4 rentals, and I never heard word one from Hertz about anything, and (knock on wood), I don't see any suspension of my rental privileges.