I don't have anyone more than 10 miles one way and I actually considered dropping those TWO because it was 40 minutes of my day spent traveling to/from, but I ended up with another one in the same area making it more worth my time.
Most of mine are within 5 miles. My average daily mileage is around "15".
I think I mowed 14 lawns last Wed and put a total of 22 miles on the truck.
I quoted one out past 15 miles once. I HAD to pad the price to account for time/gas if I planned on mowing that one, single job.
I didn't get it (because the price was higher than a local guy's price), but that was for the best in the long run.