I am very happy to hear that your fish are responding to the treatment, hopefully it will be the last time.
I just think that if you are constantly fighting infections -- of any kind, bacterial, viral, protozoan like ich, or worms -- that there is room for improvement in the fishkeeping method. I say this because my own experience has been largely disease free. When I first brought the fish home from my LFS, my fish had worm. Two full anti-worm treatments latter, and the problem was gone, forever, as in never came back. Some time back I bought a few baby tiger barbs from a different LFS. While in quarantine, they developed ich, but that is why I have a quarantine tank.
Other than that, I am talking many years without a single disease in the main tanks. I don't buy live food, since I cannot get it near where I live, so that is one possible vector that you are using that I don't. Otherwise, it sounds like I do all the other same things. I feed them frozen food, many, many different kinds as a matter of fact. Freezing does indeed kill most (if not all) worm eggs. You are thinking of the protective covers that some worm eggs have, so the egg survives the digestive acids in the body. But temperature change is the easist method to ensure that food is safe -- either freezing the food for several days, or ensuring it is cooked completely through.
My hands are defintely in the tank for maintenence. I just use my local tap water. I don't know what other differences there are.
The point is, and has been, the disease has to come from somewhere. If live food were the source, I'd either stop feeding the live food or work on culturing my own live food. If you are bringing in fish without quarantining them, then you are just opening your door to these problems. But, if you take some simple precautions, diseases should not be running rampant in your tank. They have to come from somewhere, and if they are recurring you should take it upon yourself to learn where they are coming from and stop them. Again, this isn't just theoretical, but from my own experiences. Not even just my own experiences, but from the experiences of several other members on this board that also have long-term disease-free tanks. It is not just theoretical, it can be done, you just need to eliminate ways the bugs are getting in your tank.