I wonder how "large" that percentage could possibly be. When I was little, I flew HYA to BOS almost every other weekend for three years (until I was old enough to ride the bus by myself) to see my dad. Assuming I could have earned miles on PBA or Air New England and our once- or twice-annual longish vacations were on partner airlines, I still don't think I would have reached 50K miles per year. If my dad had lived in Los Angeles instead of Boston and I kept to the same schedule, things (my potential earnings) would have been quite different, however I'm guessing the visits would have been less frequent were that the case -- unaccompanied 9 year-olds aren't exactly the most represented demographic on Sunday night redeyes. As an aside, I'm guessing that there aren't many parents out there who would deploy their children on solo mileage runs to SIN as a means to close in on the next level.