I am young-ish (34) and still try to be responsible  when I go for a run.  Young people can benefit from being a bit careful:  when I was young, I thought I was invincible when in fact I was far from it.  It's just a suggestion, obviously he can do whatever the heck he wants to do.  The way I think of it: the problem with my nose is bad enough (and may very well never go away), so I need to be extra responsible with the rest of my body.  If I get serious problems (e.g., persistent back or knee pain) in addition to my nasal symptoms, it would be that much harder for me to cope.