I would never put 1-shot on any of my sign work ever again. Two years down here and it turns to chalk. I'm all latex based on my work and it holds it color very well.
One Shot turns to chalk here too. My salt air must be like yours. LOL. Latex all the way, it lasts forever in our clime. Now inland, one shot's not such a bad idea. But on the beach, no way. You need to learn a "new way to work" so to speak, but in 16 years of doing this I think we have figured it out. I've repainted/waxed/clearcoated a bunch of one shot in that time frame, but never any latex!