I can speak from experience that UV exposure will eventually deteriorate them if something isn't done. I have a 28' one that literally had a foot break off due to UV rot. You should take care of them before this happens.
Presevation was also a big concern. This ladder is almost 18 years old, but still in good condition overall. I don't want the fiberglass strands to break down as it is a nice Type 1A with the pole rest and messenger hooks on it. I think I'm going to try the mild compound and wax and see how it goes.