I thought it was supposed to last 12 hours but I'm not sure.
Anyway, precipitated withdrawals can very it seems from being a little uncomfortable and pretty short, like half an hour, to being horrible, and pretty long, up to three or four hours, that's how I've experienced it the worst. I heard precipitated withdrawal from suboxone when coming off methadone can last a lot longer, like 6-8 hours.
It all has to do with how big your habit is, and how much suboxone you take i think. With heroin I could usually dose suboxone less than 12 hours after my last shot, and I would not get precipitated withdrawals. If I had only been using a smaller amount of heroin that usual, and I dose my suboxone too soon, I found that the precipitated withdrawal was pretty minor as my habit was pretty minor. I would feel anxious, cold/hot flashes, and some diarrhea, but it would usually end after half an hour.
The worst time I had precipitated withdrawal was when I had taken 2mg of suboxone about eight hours after my last shot of opana. I had only been using the opana for like, ten days, shooting fifty mg a day at average, but the precipitated withdrawal was horrible, and seemed like it lasted forever. I didn't check the time when it started or ended, but I know it lasted at least two hours, probably three, and then the whole next day I just felt shitty. Not withdrawal really, but a lot of anxiety/depression.