I'm running Windows 10 and I have Sketchup 7 through Sketchup 2016 installed I was using Sketchup 8 for all my developmental work. Now I use Sketchup 2016 as I like a lot of the new features. More ways to draw arcs, better tool bar handling, trays, better info when working through bugs. The other versions are simply for testing my plugins. I use a strategy where my plugins go into a shared folder that all versions of sketchup use. So I can configure a plugin and then test it on all versions of sketchup. This also makes it much easier when upgrading. When Sketchup 2016 came out all I had to do was drop a 2 line ruby file into 2016's plugin folder. All plugins loaded without having to install them.