Hello
In SimpleMemberShip Joomla membership component
ordasoft.com/os-simple-membership-joomla-membership-extension, There we have some methods for save user on your site:
1. When you create User Member Ship group, and create it as Payment, We create Recurrent payment. So Payment will renew every time when membership expire
2. In SimpleMembership you may create Menu - For Prolong Account, where User may renew self account
3. You may configure and connect to CRON send email to user and to Admin - about: some user membership expire soon
Regards
OrdaSoft Team