Sorry, didn’t get your scheme. Yes, I mean one more application installation on production server - usually I use it for tests and to check changes with the client before moving them to production.
If you use VCS (I use this scheme with git), then it’s convenient to have two main branches. Dev branch is deployed to Staging, Master branch is deployed to Production, having all current changes in temporary branches that are merged to Dev branch first (a bit more sophisticated approach is described at http://nvie.com/posts/a-successful-git-branching-model/ ). This is especially convenient if you have auto-deploy configured.