as everyone is saying, it takes as long as it takes, everyone here is dead on what occurs, & when. If there is no livestock in the tank, relax. I wouldn't even do the 70% water changes, esp if there is NO livestock to worry about. Just gives the bacteria that "eats" the stuff, more to eat. (BUFFET STYLE, ALL THEY CAN EAT!)
One time, you'll be looking at nitrites off the chart, then a few days later, "Hey.. Where did they go, they are at zero, and ammonia is at Zero, and my nitrates are climbing." THEN..
do a water change, and start stocking
SLOWLY with fish and inverts.