Watch out for leaves collecting on the slide out - sweep them away before closing
When it's retracted and below freezing it can be frozen at the mating surfaces with the trailer so don't try to open it
You can generally leave slides out during rain. All I've seen have a slight taper away to shed water
They tend to seal to the trailer during times of non-use. Some slide-lube on the mating surfaces every year goes a long way
The slides on every RV I've owned scare the hell out of me at times but have never failed. They seem to buck and flex when extending/retracting but I guess that is just what they do