The Michigan Distilleries you will find are located in some of the best spots which makes them super easy to tour without too much drive time even though there are a lot in this state, a few days at each major city should be enough to reach them all.
The Wolverine State has three main locations in which distillers seem to gather around and a lot of them line the water. Whether you live locally or are visiting, it is worth it to check them all out and be sure to frequently come back to this site as more and more of them are getting added each day. Tours typically last from 30 to 60 minutes per tour and they are well worth your time to check out the different ones. Each one has their own flavors and charm to experience.
What is even more awesome is that most distilleries offer free samples of their liquor when you go through a tour as well. The tours are extremely interesting and fun to do too. They aren't just there to sample the liquor that you're looking forward to but are actually very informative and you get to meet a lot of like-minded people usually that are also doing the tour. - Be sure to call ahead if you are planning on doing a tour at one of the distilleries to check on availability.