I reckon they could run 50-70mpw, given you could only train one hour on weekdays and maybe two on the weekends. A lot of typical high schoolers top out at 16-16:30 for 5k, so I'll say this is the pinnacle of the average hobbyjogger that really really tries given their lifestyle constraints like being a Dad or having a job, etc.
TrackBot! VDOT 16:00 5k
TrackBot! VDOT 16:30 5k