I am having a problem with expensive sunglasses bought in the US

Are they only supposed to stay clear for a year or so before being replaced?

I have a few pairs of Ray Bans and Serengetis on which there is some sort of cloudy build-up on the rear of the lenses. Cleaning gets the glasses clear again but the cloudiness comes back within a few hours.I have tried optical cloths, optical cleaner and in desperation, Windex.

This doesn't seem to happen with less expensive glasses and the cloudiness doesn't appear on a pair of Serengeti tradewinds bought in Europe about a decade ago

Does anyone regognise this symptom and have a cure please?