I wouldn't do your first water change until about 2-3 weeks after the tank is completly cycled. It's hard to say how far up all your readings will go, some of mine were off the darn chart!! But my readings were somewhat consistant, from the time my Ammonia peaked, it took 10 days to come all the way down, same with nitrite, it peaked and ten days later was down to zero agian. All and all took about 6 weeks. Seems like forever, but take it slow.