I have just over 20,000 miles on my Model 3, acquired in December, 2017. So not all that much. Delivered without fault. The only annoying problem was the weird lack of bass in the back speaker for several months, but that problem has gone away, so I guess they've fixed the software problem. Also, my daughter crashed it into an Odyssey (the front end was a mess, but it was drivable) and it was in the Tesla body shop for a couple of weeks, but it came out all good again.
Also, as it was a fairly early one, they messed with the suspension to smooth the ride, and the windshield and roof to reduce wind noise. I'm not sure whether the wind noise is all that much less, but I'm reasonably happy. It's pretty amazing the work they were willing to put in for problems that weren't all that serious.
Together, I've put over 51,000 miles on my 3 and new S (acquired about the same time) in almost a year and three quarters. Seems like a lot given that I drive them for pleasure. But they're such a pleasure to drive that I guess it makes sense.