Personally, unless you are experiencing an outbreak of ich in the tank and the fish are obviously suffering, I would just leave them be and let it runs its course. If the fish aren't eating or the "spots" are taking over their bodies, then obviously further action is required. I don't want to argue about that philosophy, i'll let you decide what to do, but it has worked for me in the past. On a side note, I do soak all my food in selcon and garlic juice though neither cures the problem, they both help the fish's immune system, which is what the fish uses to fight the parasite.
Ich doesn't necessarily remain dormant, it has a life cycle. There is a lot of information on the web so i'll let you find that info somewhere else. Just google, saltwater ich life cycle and a zillion pages will come up. But no it doesn't lie dormant and it will complete its life cycle and die off within 6 - 8 weeks in a fishless tank.
The stage that ich is in when we can actually see it is the cyst form that is a white spot on the fish, that soon will fall off to the substrate and new little parasites will be born. Think of the white spots in terms of an egg (though its not actually an egg). Cleaner shrimp and wrasses will eat those cysts, but the actual parasite is living under the skin of the fish that they can't get to. In other words, they help, but they can't properly cure the problem on their own.
UV and Ozone (if a quality piece of equipment is used) will kill the parasite in its free swimming stage, but nothing else. So it can't do anything about whats on the fish or the substrate etc.
Overall, good feeding, cleaner shrimps or wrasse, uv or ozone will make quite an army against ich and will do a lot for preventing and handling outbreaks in your system, but overall the only way to cure it is with hypo or copper for the fishes, and the absence of fish in the tank you want to cure. Its a lot of work, but if you want a truly ich free tank its the way to go. Otherwise, like I mentioned just wait it out and see what happens. I have even had delicate fish like my copperbanded butterfly have an ich outbreak and beat it on its own. If you do decide to treat one fish, you will have to go ahead and do them all otherwise your efforts will be pointless. Good luck.