I learned the hard way about registration....
My second time in MI 4 years back, my wife and I thought we would enjoy our Christmas sledding for a couple of days. We were just across the road on #3, turning back to Krupps on our last 1/4 mile of a two day trip and our DNR favorites stopped us before we crossed the road. My wife's sled was out of MN registration from the year before, so our DNR buddies wrote us a ticket for no out of state registration for $130 and told us to have a Merry Christmas! It was their last ticket of the day to meet their quota, as they went back to their station....
Know your laws of the state you are going to, otherwise, you will get a nice "Christmas Gift" too..