Our '06 Monterey did the same thing to us the first winter; left rear sagged over several weeks. Went out one day and saw a small crack on the upper passenger side of the windshield. Over the next couple weeks it got a whole lot worse, eventually shredding a slew of cracks across that side corner. I was new to diesels and air bags, much less one piece windshields, and it was a lesson.
It turned out that the glass had been mis-set at the factory, but the twist from the bag leak didn't help. I learned to dump air rather than leave it in Travel Mode when parking for any length of time, especially on any degree of unlevel surface. I often check that the cracks between closed bay doors and body are relatively even all around, an indication of no cap-stressing twist.
Joel