

I think that’s being a bit obtuse. It’s obvious that “natural” in this context means not cut short by slaughter/disease/etc. The natural lifespan of the human being is what could be said to mean how long a human lives if an early death doesn’t take them. Moreover, that range can include the tribal human living without processed food or electricity or the sheltered city dweller living safely alongside their McDonald’s.
I’d do it, but retiring early = doing my hobbies instead. Long days writing books, making art, volunteering, and pet sitting. Retiring would just mean working the jobs I want instead of the ones I have to.