Yes, I actaully agree with this, even though I am hesitant (hesitant only because I then hate it if it spikes and we've obviously dared it too, lol.) For lack of a better explanation I've begun blaming the differences in filters a bit more for the fact that some systems reach a nice solid 12-hour double zero in two months or less, whereas there seem to be 10 or 15% that take forever like this and usually still have nitrites not making it at 12 hours.
But regardless of the theories, I agree that in GG's case in particular there's just no point in going on with it. Its completely right that the two young goldfish are going to produce way, way less than 5ppm and the filter should be completely up to handling them. I know that GG will not only be cautious in adding very small additions of fish with a couple of weeks between addtions but also I fully expect him to be a great maintainer of his gravel-clean-water-changes on the weekends. So this seems a very safe case on which to pull the plug early.
You will have to watch it just as if it were a fish-in cycle, just to be on the safe side, GG. Another reason to watch it carefully is in case there is some serious flaw in the filter that we just haven't understood and that might be leading the fishless cycle to not end and would still allow too high a nitrite level. Rare but possible I guess.
By the way, I'd just like to also throw in my agreement with Caz, a number of posts back, that the rapid rise in nitrate(NO3) after a water change is indeed a very, very good sign that hints at the fishless cycle really being basically over. Any filter that is doing that is giving a good sign. Also, just like Si's and many other cases, the vast majority of ones that have become so long that we've aborted and switched to fish have behaved just as if they'd had a good qualification week. The few that have re-spiked after fish were added were usually shorter fishless cycles, in my memory.
One other benefit of switching to the goldfish (or any fish) from the ammonia after the bulk of the fishless cycling of the biofilter has already occurred is that I feel the fish and their waste do begin to help the tank have a more complex chemistry. The overall nitrogen cycle in the tank may become more smooth when there is more debris to help maintain a more regular heterotrophic population of bacteria alongside the autotrophs in the filter.
Good luck GG (if you haven't already done it before I write this, lol)
~~waterdrop~~