Irreversible? If Tom Brady can come out retirement your typical tech worker will surely find it possible.

I think it sort of is unless someone is a real name that lots of companies would fall over themselves to hire. For most tech workers--not limited to developers--if you decide to hang up your cleats in your late 50s or 60s, it's probably going to be difficult to change your mind a couple of years later. Part-time consulting is probably easier though. (Probably less so at the moment.)