DSC era that could be about right. There's the "little known, seldom-used reserve activation clause" that Kirk used to get Bones back aboard in TMP, assuming that wasn't just Kirk bluffing him.
Bear in mind though that 60 may not be a partiularly sedentary age for humans even in the DSC era though - certainly by TNG Picard was nearing 60 at the START of the series.
Okay cheers. I'm still working on details so his age may change, but I'm sadly killing him off so....*spoiler*, but thanks for the help.