Once you leave the university, your Microsoft 365 Apps for Enterprise license will be removed. At that time you will be unable to install new instances of Microsoft Office. When you are no longer eligible or deactivate a device, Microsoft Office will enter Reduced Functionality mode which only allows you to read files, you will be unable to edit. You will not lose any documents created. At that time you may purchase your own copy from any retail store or you may opt to uninstall it.