Hood underside structural braces glue issue
 

I have an "older" but pristine 98 Boxster and yesterday, after driving around (and parking) I noticed that the hood has a few slight "ripples" for lack of a better word. It looks like someone has vandalized the hood with their fists. (no paint damage) Long story short I had a terrific mobile paintless dent repair guy come to the house, this morning, to repair the damage and after 2 hours of work it now looks as good as new.

He did mention that on a lot of "older" cars the factory glue, which attaches the structural support cross members to the underside of the hoods sheet metal, can break down and come loose with age, giving it much of the same "ripple" look. I've never heard that before and just wondered if what he said was true and if any others have experienced anything like that. .......If so, is there anyway to prevent that from happening in the future?