Hi Joseph,
I don't think you can disable the guest account if the user hasn't logged in for 7 days.
You should be able to work this around based on last login timestamp of the user. Like allow access when the account is active and the user is back within 7 days since the last login.
If you are planning to disable the account after no activity for 7 days and allow the user to re-rigester, then you can achieve the same with the above workflow by redirecting the client to registration page when you find no activity for the last 7 days.