Prevent Repeat "Demo/Trial" Users

My app allows my clients to see and access certain things based on subscriptions. All “new/demo/trial” users of the app get a certain set of things free included when they first install the app. I give them 7 days to see the “normally paid” content and then turn that off and only let them continue to see the free for as long as they like. Thought about it and I log when they first login to the app via email and that is how I get the 7 day free calculation. But I had not thought of the issue of them deleting the app and reinstalling and it writing another date of entry and starting another 7 day period…any thoughts on this or am I missing something that would already track or prevent this?

If a user deletes the app, it’s not going to delete any data. They will still have a user record that will still be there when they reinstall the app and sign in again. The only loophole would be if they use different email addresses to sign in.