There he goes with the reductio ad absurdum. Slowtime does NOT demand OMD/BND or Decimation or Rebirths of any kind. Those kinds of stories are usually justified by a desire not to keep time slow, but to reverse it entirely!
Semantics. The consequence of slowing age to a standstill in any comic universe always results in regressions of character, whether it's highlighted by a big event or not. X-Men. Spider-Man. The Avengers. Fantastic Four. The
entire DC universe, more than once. I challenge you to find
one single exception, wherein a status quo has not once been shifted back to the way it was years and years ago and character progress thrown out the window in order to keep these characters relatable or whatever excuse they use this week.
Characters can easily move forward without having to turn 60 in the process. For examples, look to Batman, Spider-Man, Superman, Captain America, Dick Grayson, Tim Drake, Jason Todd, Supergirl, Lois Lane, Jimmy Olsen, the New Gods, the Justice League, the JSA, the Avengers, the Teen Titans, Blue Devil, almost every mutant in the history of the MU, Namor the Sub-Mariner, and easily 75% of the superheroes of Marvel and DC's universes.
You're mistaking change with growth. Batman and Superman have changed a lot in their history, but grown much less. Batman
changing from camp to dark, or then from dark to sci-fi, is not organic growth and development of story. All it is is a shift in genre or style. Batman himself is the same stunted 30-year old that he was since the 1940s. Sometimes writers will find new things for him to do or explore new places to take this stunted 30-year old, which is why those stories can still be good, but what's the difference between reading about Bruce Wayne's adventures ten years ago versus reading about his adventure's now? Nothing. Only some status quo changes that are eventually placed back to the way they originally were (Commissioner Gordon's "retirement," for instance), and some cast member shifts that get thrown out whenever the writers feel like they aren't "classic" enough (Cassandra Cain, Stephanie Brown, Azrael, the list goes on and on).
And some of the examples you're throwing out are, forgive me, so riduckulous that I'm not sure you're even thinking when you suggest them. Supergirl hasn't even been able to stay same
person for more than a decade, much less grow as a consistent character. Jimmy Olsen? Are you kidding? He's the classic prototype of a kid that the writers won't let grow up, and any growth is immediately undone so that he's constantly a fumbling kid sidekick. The JLA? Are you talking about the same JLA that
you yourself have complained has been letting go of the new and letting all the old back in? And Nightwing, Robin, Teen Titans, and the JSA are like the prime examples of characters who
have aged and grown and gotten all the better for it through the years, so that's really proving my point instead of yours. Or have you forgotten that half the JSA are made up of characters who were once young but are now sixty-years old?
First of all, no one's talking about characters not aging at ALL. Characters in the MU and DCU obviously do age. The common conversion is four years real-time to one year comic time. Some say 5:1, rather than 4:1. But everyone knows these characters age.
And the natural thing to happen under that parameter is that eventually, some characters would have to reach 60. I'm talking about keeping time slow, just like you. The difference is that I want time to be slow but
steady. Ten years of real world time could come down to
two years of comic book time for all I care; what I don't want is for those two gained years to be eventually forgotten about or obfuscated. Your definition of slow time is that heroes would just be stuck in indeterminate teens or twenties or thirties forever, depending on the character, all the while mainting the
illusion of forward-moving time. All that illusion does is make the problem
more apparent, as character
claim to be aging and that time has passed and yet everything is the same as it always was.
Yet even if they didn't, that wouldn't necessarily stop them from developing! Ever read Calvin & Hobbes? Those characters never aged a day, yet they developed far more than anybody in these vaunted "real-time" stories like Hellblazer and Punisher MAX and the like.
Apples and oranges. And as much as I love Calvin and Hobbes, I wouldn't tout that strip as much of an evolving story at all.
And even then, guess what? Calvin and Hobbes
ENDED. Their story has capped off, given a resolution and closure, and it's all the better for it. If the strip were still limping on today under a different artist and writer, I imagine you'd be singing a different tune. Or maybe
you wouldn't be, I dunno.