I know that Top Gun is generally considered the best of the best when it comes to awning fabrics and will last for many years. The longevity of a fabric will depend on the amount of UV exposure and in the case of Annie's cloth failure some of the cause will be the high amount of UV radiation in New Zealand, as witnessed by the fact that along with Australia we have the highest rates of skin cancer in the world.
Top Gun is quite heavy and having had a very heavy sail made from Duradon (which does not rot) I know that light weight is better when it comes to sail cloth. No one has mentioned proper sail cloth in this forum thread. I know that sailcloth generally comes in the rather boring colours of white and off white but it is the fabric built for the purpose and I suspect no more expensive than a fabric such as Top Gun. The off white Haywards sail cloth on Footprints and Tystie has built in UV protection and I love the colour, and the sail has been much admired by many people.
A sail cover is I think important to protect the monetary and time investment in our sails. It took me almost 3 days to build the sail cover for Footprints, what with all the cut outs and velcro strips to allow for lazy jacks etc, and learning how to make a sail cover as I went, but I know that a sail built of good quality Dacron, and covered when not in use will last for 10 years plus.