It is recommended that you do not assume that superseded updates should be immediately expired in favor of the new, superseding updates. As noted above, there is no guarantee that supersedence is absolute. You should allow enough time to make sure superseded updates are no longer needed by any of your client computers.

Is it safe to decline superseded updates?

Automatically Declining Superseded Updates

When you approve a new update that supersedes an existing update which is automatically approved, the superseded update becomes Not Applicable to a computer or device once the newer update has been installed. ... When that is the case, the update can be safely Declined.

Do superseded updates install?

Generally if you have superseded updates in your deployment you will see in the log files during execution that they are superseded and will not be installed, but in some cases some of them do install.