Those sailmakers were steering you right. they could have talked you into more expensive sails, but were more worried about getting you into the RIGHT sail for your purposes!
The absolute worst thing you can do to a laminate sail is use it outside it's designed wind range. The second worse thing you can do is flog them!
I am curious about this mold issue. Am I to understand that people are getting mold on laminate sails? How is that possible? How can mold grow and stick to mylar?
Mold and bacteria can stick to 'anything', and since the materials of sails are 'carbon based' the mold and bacteria under the correct wetted conditions can start using the 'panel joining glues', and the material itself as their nutrient source. Such microorganisms, under the right ambient conditions can use even metals as their nutrient source, as that is how over aeons of time large accumulations of ores were concentrated in single places .... microorganisms EATING and concentrating the metals !!!!!
If one is 'cruising', especially long distance cruising, the use of 'high end' woven dacron is unsurpassed for fatigue, strength, service life, and most importantly - SHAPING under varying windloading conditions. For coastal cruising, then a good 'cruising laminate' - laminate 'center' film covered on each 'side' with a 'taffeta' dacron scrim to protect vs. chafe is probably better, but less shape adjustability and less overall 'service life' ... because the central portion of the laminate is 'film' and the outer layers are porous, there is much less tendency to grow 'mold'.
Especially in super-wet atmospheric conditions on DACRON sails that occasionally become 'moldy' - to prevent such, simply spray on 3M "Mold Guard", works on 'sunbrella' too.
One must remember also too that full laminated sails are designed for specific wind range usage, and not very 'shape' adjustable via applied 'edge tension' .... just the opposite functionality of a high end woven dacron material.
these materials are subject to 'creep' or permanent deformation under continual load .... and as another poster so correctly stated, if you don't release halyard / outhaul, etc. tension when not
sailing, youre ultimately going to permanently stretch (permanent 'creep' distortion) the hell out of the luff/foot and that functionally changes the shape on the opposite side; hence, 'blown out' sails - unload the 'edges' when not sailing and you'll keep the designed shape of ANY sail a whole lot longer.
The ONLY real problem with woven dacron sails, especially mainsails is the need for a 3 strand 'boltrope' at the luff. Each time the boltrope is (properly) 'stretched out' to its 'as designed' length and then released (you typically NEED to stretch out a bolt roped sail by an additional 1" for every 10-11ft. of luff length when raising such a sail), the bolt rope ultimately becomes fatter and shorter .... So to compensate and prepare for this 'hysterisis' of the boltrope, have the sailmaker 'store' extra length of bolt rope at the headboard so that when the bolt rope needs 'adjustement' it can be done easily and cheaply - to restore the sail back to OEM length ... just a few $$$ to do so or can be a DIY project if you have a needle palm and sailmakers twine; otherwise without constant (every ~200 hrs.) adjustment of the bolt rope you get a 'baggy', increased draft, hooked up leech mainsail .... and ALL you have to do is 'ease' that boltrope and the sail will correct back to proper 'luff length'. Sailmakers don't like to offer mainsails with 'stored' extra bolt rope at the headboard ... they sell a hell of lot more sails that way.
Also FWIW, for UV covers, Sunbrella has been offering a 'lightweight version' for several years now especially for sail UV covers ... no more need to have all that massive UV cover weight aloft anymore.