What's funny, is that even though this strip takes place in some weird universe where the 21st Century is somewhat reminiscent of the late 1950s or 1960s with several stereotypes confusingly allowed to be maintained, the Veeblefester Tea Cozy Corporation doesn't have a retirement plan for their employees. No pension and, I would assume, no gold watch after retiring from this company after 40 years. Just a "Don't let the door hit you on the way out!"
I tried looking up this study but couldn't find it. I didn't find anything specific about time but at what age most people look their best. I mean, this joke doesn't even need to be done because Mother Gargle is at her worst all the time. As is Brutus.