Not a problem! Asking more questions, only develops further understanding. So, as far as the average goes, that is kind of tough to answer. Like previously mentioned, you can does 2ppm ammonia. I know others who do this, and it works just fine. It is the same concept, except that it just promotes the growth of a smaller colony of bacteria than dosing at 4ppm will, in my opinion. As far as starting from scratch, I am not to sure which would be quicker. The only way to realistically test this would be to have two tanks of the same volume. Does one at 4ppm and the other 2ppm. At the exact moment. Then note their results over a given period time, which could be a month. Everyone does it differently, and gets different results. It has usually been a month for me, because I use the same method and in the same fashion repeatedly. But I find safety in numbers. If I can covert 4ppm, in 24 hours, than I know for sure I can convert whatever my waste is from the intial stock. So, if the initial stock bio-load is less than 4ppm, the colony will adjust by lack of food. Yes, there will be a mass die-off, but I have yet to find evidence that leads to the death of those bacteria will cause an ammonia spike. Also, in your case, you did right to go back to your initial dosing levels. You need a constant in your research, which is the ammonia.
I hope this helps explain more! If you are still curious, just ask specifically what it is that you are curious about! The reason nitrates stay longer is because nitrates will turn to nitrogen gas. There is another group of bacteria that consume nitrates, and I would assume that they take longer to produce nitrogen gas as a by product. The nitrogen gas leaves the water surface and enters the air. Also, plants and algae utilize nitrates as well. This is a small step in the process of how we get oxygen from the ocean, which contrary to popular belief, is where most of the world's oxygen comes from. Not trees!