In following posts you say it doesn't include going home. I'm kind of in the same boat as you, living in northern Mich., just not quite as many miles. I include all miles for my numbers and I'm around the 30% range. They will affect your percentage, but you can't pretend they don't exist.
I must admit I find it quite amusing to read all the things that people pretend don't exist, or pretend certain things are not really an expense of the business, so therefore, don't count it. Others count things into their business expenses when they're clearly not. When we really WANT something, we're going to make the numbers work for us, whether they make sense to anyone else or not. It would be much kinder though, if we could let newbies know the reality before they quit their day job. The romance of the road is awfully enticing.