By having multiple versions installed in different directories, you can use any of them and know that they are isolated from each other. So, you can go grab that nightly build and know that it isn’t going to break your stable development platform. Furthermore, if you follow a couple of simple steps, the platform will also update its plugins.
If you want to try a new build, simply download it and install it. After this, just start the application. The application will then detect and ask if you want to import settings from a previous version. Once the application fully opens, it will then look at any installed plugins from previous versions and ask if you want to import them. It will also warn you if an older plugin isn’t compatible with the new build.
So, in the end all you really need to do is run the new build before you uninstall any previous builds. Eventually, you will need to uninstall old builds, but there really isn’t any rush since they are isolated.
Have fun and go grab the newest build of Netbeans.