Like anything else, they wear out over time.
I've owned my Rodeo for 3 years now and the lift struts on my hatch have always worked fine, until this winter. Now, they will not hold the glass up since the weather has turned cold.
I've seen them at the local auto parts store, so you will be able to replace them without going to the dealer.
The only thing you can do is replace the struts, I'll be doing mine soon.
http://www.partsamerica.com/ProductL...=Lift+Supports
Dale