seems like they can stay that way for weeks! But yeah, sometimes they will pip, nap for up to 24 hrs then burst into a flurry of activity.......usually when you walk away from the bator.
Be excited! Cheer them on! but let them do their work on their own, they know what they are doing.
Came home tonight, had 4 new chicks in the incubator, 4 eggs pipping. Ate dinner, had 6 chicks and 7 pipping. I just go and check on them every hour and make note of their progress. One pipped and zipped in about 30 minutes. Another one has just been taking its own sweet time since 6pm.