With macOS Sierra recently released the media are very keen to help everybody do a clean install. It's better. It tends to make your mac run really fast for several months or more, and many people report that it fixes longstanding issues that they previously had.
Personally I do a clean install about twice a year, and every time I install a new major OS X version. I describe exactly how I do that on the page that this product hunt post is linking to if you need any further help.