You have something else going on here. Brightside will chalk a bit after a few years, but I have a Hobie Cat that I painted the decks on with Brightside eleven years ago. Since that day, it's been sitting on a beach in northern Wisconsin 24/7, year-round. I also painted a small chunk of my garage with it and some outside window trim five or six years ago and they're all doing just fine. The Hobie is fairly dull, but still has enough remaining paint thickness that 20 minutes with polishing compound and a buffer would make it look great.
If this is a wood/canvas canoe, you do have the problem that your Brightside is applied over a moisture absorbant material (canvas) which has only been partially saturated with filler. This doesn't make for a particularly stable base for paint (especially alkyd enamel types, even with polyurethane added) compared to a more stable, fiberglass or properly-primed wooden surface. Alligatoring is generally caused by the material underneath the paint shrinking. Paint will usually expand and contract to some extent along with the base material, but does have it's limits. Once the base has moved past that point, the paint alligators or cracks. The possibility of water intrusion from inside the canoe could throw another potential monkey wrench into the equation as could some sort of incompatability problem between the filler formula and the paint formula.
In any case, by now if it's spent enough time outside, the Brightside might be starting to get a little dull looking, but nothing a little bit of a cleaner/wax like 3M "One Step" and an old towel couldn't fix in short order. The problem is likely not the paint, but some sort of combination of factors.
