Your wrong. how do you know exactly why your fish died. did it tell you it was getting stressed by someone else? if you did water changes, maybe the fish could deal with the additional stress the other fish are putting on it.
You say you havent lost a fish in 17 weeks... is that good? I have a saltwater tank. 12 fish, including multiple dwarfs and tangs. I havent lost a fish in over 2 years. Why? water changes.
to say it can be done, is one thing. you can marry your sister. it can be done, but should you?

I haven't finished reading the thread yet but I'm just not comfortable with the idea of never doing water changes. I've heard of people not doing a water change for a month or two (usually people with densely planted tanks and low stock) but not ever doing water changes....even if you're replacing a few gallons a week and therefore all the water volume is essentially replaced every year, that's still a long time for the fish to be in the same water.

I would've thought there were more bad things that could be in the water than just the usual few things that are tested for but I haven't looked into it, nor do I have experience of maintaining a tank without water changes, so... just my two cents.

Seems like mother nature has her own ways , but if we are talking of water change than not only the way in but the water must have the way out , vaporizing waste ? on less if fish starves and eats its waste . With no water change aquarium good for frogs only .