Plastic shroud covers OK or not?

[bwindrope]

I've searched the forum and nothing comes up for this so here goes. I've just replaced all my standing rigging (myself, a different story) and also happen to have just replaced my genoa sheets. Noticing after just a few sails that the cover on the sheets is already getting all fuzzed up, even though the wire is new and slick.

So, the question is, is it OK to put those plastic covers on the shroud wire or does that limit oxygen too much to the stainless and cause corrosion. If they are not OK, what else is better? Looking around my port here in Friday Harbor, I notice most boats just have bare wire, but shoot, I don't want to go through sheets every few months...

Any help appreciated.