When your main gets old

Not everyone can afford a brand new main every season. Most people are racing with mains that are two, three or four years old. Many of these sails don't look too great, but you can make an old sail go faster.

As mainsails age, they generally get tighter leeched, draft-aft and fuller. This means you should compensate with the following:
 

Use more mast bend to remove bagginess from the middle of the sail.

Use more cunningham to pull the draft forward.

Be careful not to over-trim the main sheet.

Batten retrofit
There are several ways you can breathe more racing life into aweathered main. One of these is to have your sailmaker retrofit to the longest possible battens.  Extending the battens into the low-load area of the sail can do wonders for that wrinkled, baggy look.

Re-cut the sail
Another suggestion is to take photos of your main in action, and show these to your sailmaker. Often they can perform a face-lift that will move some of the draft from the back to the front again.

Sail care
Treat your main well so it will stay fast as long as possible. Don't let it flog in the wind.  Fold the main sail well after each day's use..

Sources:

(1) www.arklowsc.ie

(2) Annapolis Guide to Seamanship