we are in SD also and pretty much everyone I know in the area is on a 3-4 year haul out routine. We had ours last hauled June 2008 and now are saying its looking like time soon...we'll probably wait until the yards are wanting the business more (January?) and see if we can get a deal. Monthly divers make a difference, there are some good ones but lots of bad ones too; so if they are doing a good job you can depend on them to give you feedback.