IDK if the coolant conditioner is a multi-time use thing. I had normal coolant loss in my bulletproof 2.2L '97, known as one of the sturdiest units they made. The determination was that there was some porosity in the AL itself and it would basically "sweat" out of the block. This was fixed, by my, with 1/3 bottle of some stop leak stuff. Nissan had a similar issue, and at the time it was rumored on this forum that GM had figured it out and their Factory Fill included something similar. I noted that the engine frequently had a very, very VERY mild coolant smell, but no leaks. The pathfinder my wife drove was the same. My dad's frontier also. So, I don't think the coolant goo has any relation to the HG lifespan in the subies... and don't know if it's needed during a refill. It might be needed if a flush solvent is used, tho...
M