Never had one, never carry a ladder, never climb up to clean the top of the slide, never had a problem.
If i park under a tree that looks like it might drop stuff I'll figure out a way to take a peak (stand on tailgate, find a good angle somewhere...) or just pay close attention while closing it. in 4 years going on 15+ trips per year in the wooded northwest I've never needed to remove anything.
Even if something was up there and you closed it I highly doubt you'd break anything (I may be wrong). I forgot to close a cabinet door and pulled the slide in once. the slide stopped when it hit the door, didn't even leave a mark.
The reason I don't have them, camped next to a guy with one on a very windy night once and had to listen to it all night... in the morning it was trashed.
Maybe some day I'll have a problem and change my mind? until then, the risk of damage is acceptable and potential cost of repair is probably about the same as the awning.
And I just knocked on some wood...