You can’t bring rayos from individual stories. Most people can’t work half a day.
Besides, if you think that’s ideal, why do you look to have him retire young and learn full time? Let him work half a day as long as he’s physically able. You obviously do recognize the chashivus of learning (full time).
Ela mai, financial necessity? I never disagreed with the idea that at some point, the vast majority of kollel guys must (and do) go to work (I’m referring to chu”l where military duties don’t factor in).
I also think that if one were to be faced with the option to dedicate younger years to learning or plan to retire young and dedicate later years, he should choose the former (for a number of reasons).