It really all depends on the make and model of the shoe. Possibly even how it was stored.. The shoes with the visible air sole in the heel seem more prone to cracking. As if air can leak into the middle of the midsole and do damage from the inside out. Take your Jordan IV for example. Crumbling seems to happen near the airbag in the rear of the shoe on the 99 retros. Don't the flight 89s have a jordan III midsole?
I own some older bo jackson sc trainer retros dating back to 1998. They were all bought used within the past 5 years so it's hard to say how or why they are still holding up to this day. They have the visible airbag in the rear. I had a 1997 sc trainer raider that started showing signs of crumbling. That pair appeared to be barely used before I purchased it. So I had one casuality out of 4 other survivors with nothing seemingly different about them.
I've unDSed 3-4 2000 air trainers the past few months/years, and they are doing okay. They have a straight foam midsole though with no visible air. Lots of glue issues though, like the midsole coming undone from the upper. but again, its not every shoe at the same time, or in the same place. The biggest factor I've seen with 10 year old shoes is glue. If that's your only issue on the older shoes you own, you should be okay. I would avoid shoes with visible air bags in the back though. They just seem like nothing but trouble. But a lot of other shoes should be fine.