I have never liked the idea of "giving" the first 50 miles (or 10, 20, 100, etc). It may be a good thing to pitch to a customer, but in real life there are no "free" miles. If you give away, say 100 miles a week, that's over 5000 miles a year. About 5% if you run 100k. Now, I just don't get 5%...