...Is becoming increasingly stronger for me.
In fact, I think this is the logical conclusion and solution to the various continuity-problems and such that comes with the ambition to try and make a Superman-continuity where "everything counts".
Superman himself has enhanced longevity - in fact, I believe it's mentioned in various continuities that Kryptonians live longer even naturally - mentally and PHYSICALLY perfect Supermen and all that.
We saw this in the web-comic-series "Adventures of Superman" pulled off brilliantly - how Superman begins in the 1940's, and continues, PAST modern time, into the far future... into the very end of time.
We could even have it so that not all of the supporting characters are as defunct physically either - Lois for instance could be depicted more as a woman in her 50's, thanks to some compound or another which Superman exposed her to. (perhaps the elixir of life from Superman: Beyond even!)
Jimmy could be a man in a similar constitution, perhaps as a result of his many super-powered transformations. (Elastic Lad, anyone?! It would make sense if his moldable power would keep him from aging, reconstituting him)
Some people would of course, alas, be dead... for instance, the Kents, Perry White (Clark's SECOND editor...! Daily Star reinstated in continuity).
It would also, imho, provide a perfect explanation for the classic costume, SHORTer cape and all, being the current - because he really HAS been fighting for Truth, Justice and the 'American Way' ever since 1938!
Of course, the ultimate question then becomes... should he be called Kal-El, or... KAL-*L*?! ; )
Therein lies the final battle. I'm afraid that I'm of the opinion that it should be Kal-L - the first Superman.
Editors note: A nonagenarian is a person in their 90's - closing in on a hundred years old.