Unfortunately it could be done today or it could be done 2 weeks from today, it's different for everyone. One thing you can do is slow down the feedings. The nitrite is the waste product of the good bacteria that is eating the ammonia. So if there is a lot of ammonia (food, waste from fish, etc.) then there will be an equal amount of nitrite until the good bacteria that eat that and produce
nitrate have a chance to grow (by the way, they grow slower then the ammonia converting bacteria). So if you lessen (not remove completely of course) the amount of food being fed, then there won't be as much waste from the fish, which means less ammonia, which means less nitrite, which means less nitrate

And if you are using that bottle Prime that you finally was able to receive, then that's why they are living through this

. Works pretty well doesn't it. If you aren't then man those are hardy fish.