Originally Posted by Six jours

This is the classic "European bike racer" advice. Nothing is too much as long as it's coming from him, and not some outside pressure.

"European bike racer" advice also holds that he shouldn't even have the option of being a gear masher at this age. They (and I) would have you remove the big ring entirely and either replace the cogset or set the derailleur to limit him to no more than perhaps the 16 cog.

HTH!