it varies by individual from what i can tell. generally i snort. coming off 160+mg/day this last time, i only needed to snort about 1 mg the first day, maybe .5-1 the next day, then i skipped a day, did .5 yesterday, and here i am at almost 6pm today, having done nothing at all yet. so for me, snorting lasts fine. other people like to split their doses up smaller so they can do it multiple times throughout the day, and others simply require larger amounts, depending on their original habits and how long they have been taking bupe at what mg. it's supposed to not last as long when snorted, but i haven't really had any problems.