Originally Posted by haiqu
If sails are used carefully then 5 years is very achievable. Most sails today will have a plastic layer "calendered" into the material when they are new, and a good rule of thumb is that once that layer is gone, the cloth will be softening, destabilizing, taking UV damage and starting to need replacement.
I think Rob talks about racing sails or sails for the harbor sailors.
Cruising Dacron sails have been made the same way since the middle 1960's. Lots of weight of woven Dacron cloth and very little plastic. Racing sails and cheaper cruising fabrics have a thicker plastic layer on them but less substance in the cloth for the same official weight of sails as cloth for highest quality cruising sails.
It is pretty common for even the cheapest of cruising sails to last 5 to 10 years and more than a circumnavigation. Nicer ones with better materials and construction more commonly last 10 to 15 years. Very overbuilt ones can and do last 30 years.
Proper care is to prevent chafe, have good sail covers and use them, don't let sails flog.