I don't think that these vents have that problem. I live in FL and my current boat sits in a slip year round. It's a 2000 model and has the same vents (I believe they are original). These vents are slightly flexible (rubberized comes to mind) and haven't shown a bit of degradation in the FL sun. However, they act like a petri dish and develop a lot of mold (vinegar and water take care of it easily).
canoedave wrote:i am a little concerned about the recomended vents being pvc my experiance is after a few years uv rays and pvc dont mix and the sun usally wins ! being very new to sailing not sure of the options anyone use anything different ?