What we sold was software that customers deploy locally. We don't have any of their data. But the software would stop working if their license is no longer vali

What we sold was software that customers deploy locally. We don't have any of their data. But the software would stop working if their license is no longer valid, resulting in downtime. That already made people angry enough. Now we have changed it so that the software never turns off even if license has expired (though it will continue to nag an email address). Updates also cannot be installed.