For those who have been out there - do you find enough riding to do for 4-5 days? We were looking into going out there in February this year but went another direction. From the reports, the conditions were excellent.
Also, do you find you need to change up clutch weights? Seems like the elevation is enough you'd be better off doing it.
Jetting is required (if running carbs). Clutch weights you can typically get away with keeping sea level. Might not be pulling max RPMs but most do not mind. I keep a set in the trailer just in case, but have never needed to change them out. Made two trips out there this season and five times throughout the years. My absolute favorite place to ride. My biggest advice would be that you can't "plan" a trip to The Hills as they can be very un-predictable on snow. Their last two seasons have been awesome, but hit / miss prior years. If you want to ride good pow out there you have to pull the trigger when they get a good dump. And... You can't go by the in-town forecasts (Lead, Deadwood or Rapid City). There is a significant elevation change --- in-town may get a dusting while they get 12+" up on The Hill. Call the local resorts for a good report or watch Trailshead Lodge webcam.
Regarding # of days, three is tops unless a big storm roles in later part of your trip. There are 350 miles of trails, but some are not full loops, so you do have to back-track / re-ride the same trails to get from here to there a fair amount of time. That said, the trails are absolutely AMAZING so re-riding them is not a problem. Trail 2c down to 2k is our fav - Goes into the Black Fox Campground Area National Forest. Bluffs, streams, etc. Great trail to slow down and take in the sites!!!