2008 Denali XL here. Purchased in '14 and like yours, literally overnight, it was peeling like a sunburnt hairless cat in 2018. I was patient and waited for the inevitable, a minor traffic collision. I paid $600 to have the clear redone on the hood when my door was repainted. It didn't work, the hood kept peeling. The shop resprayed the entire hood after that for no additional charge. It was PPG paint.
On a 07, 08 or 09 w/ a 6.2L, you're more likely to recoup the cost of having the roof and hood respayed. GM got it right with no AFM on the 6.2L til 09. 250K on those drivelines is not uncommon. As far as the roof, I had only the front portion around the windshield and sunroof resprayed for $350. The entire roof would of been at least one large here in Cali. Beware of letting the clear go unchecked on the roof. There is a point of no return where you'll rust through and mold will start in the headliner. Obviously, in a heavy rain state, with snow and salt, it would happen faster than a garaged truck in AZ or SoCal.
IMHO bite the bullet and get it done regardless. Make a friend at an auto body shop or local high school / college that teaches body work. With time on your side it's something that can be done on a cash deal for a grand or less here in Cali. It would be even less if you're truck was in for other body work like an insurance claim. Plan, plan, plan and be ready to bite the bullet when the time is right.
