Typically 7-8weeks for any bone to heal. If you smoke, it takes a lot longer or may even have a mal-union. It usually quits hurting after 3-4wks unless you tweak it constantly. If it dislocated (usually the sharp end pointing up towards the rectum), you don't want to know the procedure on how to re-locate it... (just thinking about it makes me shiver)
Broke my tailbone while riding a 10 feet barrel during hurricane Katrina. to add from the advices above, you may want to avoid wearing jeans, maybe try some pants with a thinner fabric so it puts less pressure on it while seating. Also you can try a memory foam cushion if the pain is really bad. And next time you snowboard buy a hips protective gear.