I have 3. I got them all small. One i've had over a year, no problems. The other 2 about 8 months no problems. 1 get the **** kicked out of it by the other 2, and is the main target for my RTG. It's tough. I really don't do anything other than change water every week.
I don't see what the so called problems with NTTs are.
I read a lot about gill fluks in small NTTs on here so i think the problems people have with them are problems even before they get them home. The guy i buy my NTTs of always has them in a medicated tank. You do need to remember they are all wild caught and put together in big tanks before being shipped.
IMHO if you want an NTT you should has a seperate tank so you can give it treatment for anything it might have as soon as you get it home and before you put it in your main tank.
My NTTs are all strong.