I have a park trailer with two slides and no slide out awnings. I leave the slides open from April 1 - November 1. I get up on the roof at least once a month to clean off debris and clean the gutters out and I will also get up after a heavy rainstorm to sweep the water off of the slides. My roof has a 12 year warranty and this includes the roof on the slides. As I get close to that warranty expiring or less comfortable climbing on the roof, I may go for the slide out awnings.
Some folks place an inflatable ball between their slides and the awnings in order to help the water run off better. I don't have any advice to offer regarding snow and ice. I am sure others on the forum do.