Have you considered using a database product like Airtable, SmartSuite, or Notion (there are a bunch to choose from) to help you organize this information?
You could still use Make to input new members in the database along with any dates or other relevant information.
Make could also help keep the database updated when changes are made to members.
The database can automatically calculate “days since” against a particular date using a formula and, when a certain number has been reached, kick off another automation to start sending emails, etc…
I know this isn’t what you’re asking for, but I feel like something like this would help with your use case and just wanted to mention it!