Ozone is just another form of oxygen, and any oxygen exposure ages polymers including what you think is rubber. Best ways to prevent that are by storing the radio in a sealed bag, like a mylar bag, available for long term food storage, gun storage, and other purposes. You add in an "oxygen absorber" and a desiccant before you seal the bag, and the aging mainly stops.
You can also use plain talc (yes, talc) which will help seal out oxygen from the "rubber" and is otherwise inert. But most folks would use ArmorAll or a similar product. I prefer the original white formula. Those protectants also actively replace the plasticizers that normally will sublimate out of the "rubbers". Problem is, they also can cause some paints to lift, if they were not properly bonded to begin with.
Mylar bag, absorbers, sealed, there's only so much you can do. And that should keep them for 20 years, unless they were made with improperly cured junk to being with. In that case, preservation is simply not possible.