I'm old enough to have bought and kept the first printing of Crisis on Infinite Earths, and some tie-ins and follow-ups, and everyone thought that was the cleaning up of the DC multiverse. Now, twenty years later, there's another infinite crisis, to clean up the clutter left after the cleanup from the first one.
In twenty years, when most of us may still be around, the current Superman will be as old as Kal-L from Earth-2, the JLA would have been around as long as the JSA was during the first Infinite Crisis, and there would be lots of other clutter, from Elseworld stories to alternate endings, all of which must be merged again.
So I'm going to ask, are we going to see an infinite number of Infinite Crises? I had always liked the multiverse, by the way, but I can see why the DC editors did what they did.
Yeah, I think we'll be seeing a Crisis pop up every 10 to 20 years for as long as the continuity-centric DC comics are published. If you're going to have that many books published every month, each carrying around decades worth of continuity with them, you've got to do some tweaking and revamping every few years in order to keep the characters appealing.
The aging thing is kinda secondary. It doesn't matter if its the 70s, 80s, 90s or today, superheroes will always have been around for about 10 years or so and Superman & Batman will always be around 35 years old.