I have a friend that has been doing this since he was an athlete in college (started at 20). He is now 32.
The only difference is he is a not a titty-baby and runs 1 mile for every year. This year he'll run 33 miles on his birthday.
He says after 50 he'll start running 1 less (49 miles on his 51 birthday).
He lives in Southeast Texas and his birthday is in August. Anyone who has ever trained in the southeastern part of the country during the summer months knows how miserable it is to do a long run in August.
If you really want to make this a challenge, at least do it with 400 repeats with a minute rest. One 400 for every year.