Your sails can wear out quickly or last for years, depending upon how you care for them. Here are some tips from Jonathan Bartlett of North Sails:

• Don't flog your sails, by letting them flap hard for any length of time when you're motoring directly into a fresh breeze. It really gives them a beating. Instead, unless you're actually raising or lowering your sails, steer slightly off the wind until the flapping stops. Or else douse your sails completely and stow them in sailbags.
• Keep your sails out of sunlight. Burn from the sun's ultra–violet rays weakens the sailcloth and stitching. You can't help exposing your sails to the sun when you're actually under way, but once you've anchored or docked, take them down and stow them in their sailbags. Your roller–furling sail should have a special edging to protect them from UV rays once they're rolled up.
• Give your sails an annual checkup–and a cleaning. Just before you put your boat away for the year, take in your sails to have an expert look them over and mend any tears or frays. You may not need to wash your sails every year, but you should make sure they're free of salt residue, which can cause the sail to deteriorate.
• Take your sails off the boat during the winter. Leaving them on the boat–as too many boat owners seem to do–subjects them to wide changes in temperature and humidity, which expands and contracts the yarns and stitching and weakens them. If your sails are dirty as well, leaving them on board only exacerbates the problem. They'll be wearing out just by sitting there.