I could never find a good solution to it. Back in the day, Rob Eye recommended peeling all the plastic off and repainting it, but like you, I didn't like the idea of eliminating the window sweep.
Just have to keep your eye out for a set of good ones. Freeze cycles and salt DEFINITELY do them in. The ones on my '01 are perfect except for one small nick in the hard plastic on my driver's window, and I think I did that with an ice scraper by accident. The car never saw salt or winter driving, so I'm guessing that's what keeps them in nice shape.