In the UK older high school kids will go on Duke of Edinburgh expeditions where Gold is the highest level, and they are going 14 miles a day carrying packs. That is young, healthy 17-year-olds. I deliberately didn't do it because I wasn't fit enough.

I'm only 38 now but I wouldn't keep up with those youngsters. 10 miles is a good day's walk for a normal person, or 6 miles for a pleasure walk.