How long do entries stay in the Unblock List of CIS

If there are entries in the CIS v10 Unblock list that we do not want to unblock, how long do they stay there?

Are they automatically deleted? There is no purge or delete button. The only way to do so is to press Unblock but this would allow the malware to run next time.

For now indefinitely. The next major release should have options to purge and delete. The list building up indefinitely is a bit of an annoyance which I am also waiting to be resolved.