This is what 18 months on a furler will do to your sail. At a rough guess this sail is worth $5000, yet when it came to me it was as you see below. What you can't tell though is the stink, the amount of water in the sail, or see the little critters that ran out as we unrolled it!
A couple of points come to mind here, firstly if you are not going to use your sails for a length of time, then get them off the rig and put them below out of the weather; a length of time would be in my opinion (and remember we all have one) would be a month. Secondly, this sail is a laminated one, the fabric is fantastic in strength and shape, yet sadly sailmakers do not recommend getting them wet, go figure that!
As soon as the laminate is sewn, the needle leaves tiny holes for the water to wick through, thus you see mold appear in the laminate.
So what to do; laminate sails should be sprayed in SailkotePlus when new to help prevent the mold appearing in the first place, and you need to go sailing a lot more often to keep the sails dry.