It might sound simple, but having seen hundreds of sails over the past few years, I have a reasonable appreciation of what goes wrong when the headsail is furled incorrectly.
A furled headsail lives outside in the UV, weather and pollution. There is a sacrificial UV strip down the leech and foot of the sail, this needs to be on the outside of the sail, yes many sails are furled incorrectly so the protected side is on the inside thus doing no good. The furl shouldn't have any folds in it either this will have the same effect of no UV strip. The easy way to see this is if you have a coloured UV strip, and your sail looks like the 'twirly' light outside a barber shop, then its furled incorrectly.
Wrap a few extra turns on the drum so that the sheets will go around the sail a few times, prevents the clew from being exposed even just a little bit and the resultant UV damage.
A tight furl will also help stop the cockys from gripping the sail and munching away at the UV, yep they love it, dunno why but I see plenty of sails damaged by cockys.
Not much you can do to prevent the pollution getting on the sail, but an annual Vacuwash of the sail will stop any accumulation of dirt. Combine a wash with a coating of SailkotePlus and many of the above problems will disappear.