The purchase price allows you to use that version of the software forever. Your license is assigned to your name and email address within our database. If you lose your software, or if you need to move it to a new computer, simply contact the support team and they will be happy to assist you.
In addition, we provide free minor updates to the software including bug fixes and improvements to the interface and to the quality of the output. You can set your software to check for these automatically or you can check yourself from within the help menu.