
From time to time I tend to think about this. Especially when I happen to be watching a movie on really the tail end (or very end) of an actor's career. Comedians especially. You just find yourself saying "It's just not the same". The Marx Brothers and the Three Stooges are the best example of "living past their prime". For the Marx Brothers probably their last pure film was Night in Casablanca. Which wasn't a perfect film. But it still had that faint glimmer of their glory days. You can see with their last film "Love Happy" it's just not there anymore. Groucho's not even bothering to put on the old greasepaint mustache and eyebrows.
I suppose to be fair, Love Happy was really a vehicle for Harpo but I believe it became a Marx Brothers film to once again get Chico out of gambling debt. Which was the reason A Night in Casablanca was made.
But even the films following it, it's not the same Groucho anymore. The sharp wit of Duck Soup and Horse Feathers has been replaced by what appears to be a very caustic and cranky old man.

The Stooges are another example of that. After Curly died they were able to continue on with the help of Shemp returning to the group. And even after Shemp died they were able to complete the remaining films with unused footage and a technique of showing another actor from behind which has been referred to by Sam and Ivan Raimi as a "Fake Shemp".
I'll talk about that more in a future blog. It's actually rather fascinating.
But the later films with Joe Besser and later Curly Joe are just unwatchable. And you can see it in their faces. It's just not that same energy and excitement of their earlier films with Curly. And it's almost depressing to watch.
And there was talk about a new line-up of the Stooges after Larry Fine had died which would have starred in... brace yourself... an R-Rated sex comedy!

Moe died before both this incarnation and the movie starring the Three Stooges could be realized. The movie itself, however, ended up being produced as
Blazing Stewardesses and starred the surviving Ritz Brothers.

I suppose it's easy for you or I being on the outside looking in to say "Yeah, they're washed up! They shoulda hung up the baggy pants and put away the greasepaint a long time ago".
Then again, I don't know if there are many young actors or actresses in Hollywood nowadays we will be debating this subject years for now. I mean really! Sit down and think about it for a little while. How many young actors and actresses out there can you think of have the staying power of a Carey Grant or a Katherine Hepburn? I'm not even sure if I can count that many on my fingers.
But back to my original point. I think a great deal of this was to do with the fact that many of these acts were really doing the same schtick they were doing when they were young. I think seeing a 70 year old still trying to do the same pratfalls as when he was a 30 or 40 year old just isn't the same.

How do you want to remember Mae West? Trading barbs and double-entendres with WC Fields. Or as the plastic surgery nightmare she would later become?

The only comedian I think really worked well into his later years (not counting George Burns because I think he was always an old man) was Charlie Chaplin. But I think a great deal of that was to do with the fact he was not still playing the Tramp well into his sixties and seventies. And I think he knew when it was the right time to retire that character. It would have been somewhat sad to see this fat little old man with white hair still trying to pull off the floppy shoes and derby while trying to squeeze into his old Tramp costume. Unlike many of the people I mentioned above, Chaplin seemed to age with the characters he played in his later films. Not to mention he seemed to go out of his way to go with parts that were out of character for him.

Even one of his later films Limelight which he played a Tramp-like character he played a performer nearing the end of his life trying to grab that one last shot at old glory.

Which is even more poignant to see him acting this out with his one film rival (or contemporary) Buster Keaton. It's a great scene of these two old school comedians who took somewhat different approaches to their characters.
I suppose I didn't really give much of an answer to the original question. But then again it really wouldn't be an answer as much as my own personal opinion. I suppose it's not so much hanging up the towel but evolving. And as much as I enjoyed the Stooges or Groucho they never really evolved from what they were originally doing when they were younger.
But at the same time, their later years do not ruin those earlier performances. And I suppose that's because despite their decline at the end of their career, they did something that was timeless and memorable.
I kind of wonder how many young comedians can say the same?