Can fly lines go "bad" on the shelf?

You guys are the reason I fish alone...

Randy wrote:
All,

I'm just about to pick up a new fly line and was checking out the prices
on Ebay for fun. Lines are VERY cheap on Ebay. Its makes me wonder if
somebody buys these lines as closeouts because they are being rotated
off shelves? I know that lines deteriorate after a few seasons of use
but do they go bad just sitting on the shelf for a couple of years? I've
heard that you dont want to use old leader or tippet material, I wonder
if the same is true for lines?

TIA,

Randy