With the Warning system, you can add a group when Warning Action is triggered or directly with a Warning. The Warning has it's own expiry date, and so does the temp group change. However, from testing when a warning is deleted/expired before the expiry date on the group change the added group isn't removed. Running the various cron tasks doesn't appear to help. The idea behind this is to allow user posting rights to some nodes to be removed and then restored when the warning is deleted or expires.