Extensive research and study have already been done by scientists. Please read the ich stickies in this forum to understand the scientific side of this parasite as well as its life cycle, instead of going with pure personal experience. Your experience may not apply to others. It IS possible to eliminate ich. All that's needed is a rigorous protocol to "beat" its life cycle. Ich needs food (in this case, fish) and it has already been proven that it dies within 18-24 hours if it cannot attach to a fish host. What does this tell us? Simply leaving a tank fallow for 10 weeks (longest observed complete ich cycle is 72 days in 32F of water) will eliminate all of the ich. So yes it IS possible to rid a tank of ich.
When you buy a fish and it comes in with ich, only two methods are proven to kill the new born theronts in the water: copper and hyposalinity (1.008-1.009, or 11-12ppt). Once you set up a new tank with live rocks, invertebrates, etc., leave it fallow for 10 weeks and the DT will be ich free. Then, buy new fish, QT them, treat them with either copper or hyposalinity for 4 weeks. Observe for another couple of weeks to make sure the fish is disease-free. Put the fish in the DT and it will still be ich free. It's a lot of work I know, but that's the only possible way to guarantee an ich-free tank. Many experienced aquarists practice this regimen (myself included) and have ich-free tanks.
"Managing ich" will work for a while, maybe even a few years, but as soon as a major stress happens (broken heater, power outage, etc.), the fish will be stressed enough that ich will take over the weakened immune system and kill fish. I have seen this first-hand in my own tank, and it happened in merely a week.
I will also make one note. Ich is truly a parasite that takes advantage of the confined environment. In the wild, even if fish contracts ich, it can swim away before the new theronts are formed and find opportunity to attach to it. In an aquarium, fish have no where to hide, so most of the theronts can find a fish host easily. This situation is exacerbated especially in small aquariums with heavy stockings. That's what makes this supposedly relatively harmless parasite so rampant and deadly in this hobby. When a tank is full of fish, theronts can find hosts quite easily, and can reproduce fast and take over the tank. This is the reason why it is not a good idea to "manage ich," simply because that's what happens when a major stress happens and fish's immune system is weakened.