You could probably use the regular subscription module for that, if you're not tying it into an automated user management system like PLESK. If you did need to tie it into a user management system, it would be a bit trickier. You'd need to write a variation of the module for that purpose.
Getting back into x-cart dev after a long hiatus. Modded lots of x-carts from version 3.1.x to 4.1.x. Developer of ImageScaler mod, Pre-login per user coupon mod, Wordpress feed mod, DigitalSubscriptions mod, Phonetic bulk download keys addon for DownloadExpander mod, Serial Number Generator for ESD products, Custom CMS/LMS integrations, external products mod, and more.