Juju, I feel your pain.
From day one of my tank, I had a reading of .25ppm of Nitrites, that only in week 7 of a fishy cycle did they finally drop. However where Nitrites are yoru issue, Ammonia was mine!
About week 4, my Ammonia zoomed up within a matter of 3 days to unreadable numbers. I was doing water changes daily for almost 2 weeks, cut back on fish feeding, etc.! Boy I was scared my danio's weren't gonna make it, and my patience level was tested.
About the beginning of last week (week 7), the Ammonia finally became readable again, and has been dropping slowly. Now, at the beginning of week 8, my Ammonia is reading about 1.0ppm (stalled there the last few days) for some reason.
So yes, time is a killer. Someone reminded me of the old cliche: A watched pot never boils.
Anyway, my fish are still alive, but I've maintained the feeding once a day rule now instead of twice, and they seem fine.