I think as a general rule of thumb laminate sails have about half the life span of dacron. Call it 10-12 yrs. (Dacron is typically blown out by then and should probably be replaced then also.) UV and water are bad things for laminate sails. Water intrusion will cause mildew to form between the laminate layers over time. (gets in thru the stiching) The mildew generally can't be cleaned and you can't get rid of it. UV will cause the layers to delaminate and the sail to fail over time. I have also learned (I got a new laminate genoa this year.) that the laminate sails don't stretch as much in gusty conditions and are generally less forgiving. Thats the bad news. The good news is that the sail will hold its shape and not stretch out basically for its entire life-span. It will hold its intended shape right up until the day it blows apart.
Maxum 3200 Miss Adventure
Formerly - Tartan 34C Yawl