There are lots of people here who are far more of an authority than I am. Especially since I'm pretty much a newbie...
however....
looking at this video...it's pretty clear that the cables were still up when there was still a fair bit of snow. And the second video is from 2008 and the top of the cables are in a bit of disarray. The broken part of the cables from 2008 were in the same broken configuration a month ago. So, I am pretty sure that they don't get removed and replaced every season.
http://www.youtube.com/watch?v=nmdw40izjcghttp://www.youtube.com/watch?v=pnUoolapBrc
