XF 1.2 Display signatures of certain usergroups only


Active member
I have a 12 month paid member option on my forum and I only want these paid members' signatures to be displayed. I have noticed once they create a signature, even if their paid membership expires their signature is still visible on their posts and profiles etc. So how can I hide/allow the signature display for certain usergroups? The user permissions for signature seem to only control the editing of them. I don't want to delete them from the database in case they renew their membership and they need to be displayed again.