When you set a rule to expire using a Time Object the rule is not deleted; it is effectively disabled. This means that once the time object expires, the rule will no longer be enforced in the policy, but it remains in the Rule Base. If you want to re-enable the rule, you would need to update the time object or create a new one.
R81.20 SmartConsole Online Help:
https://sc1.checkpoint.com/documents/R81.20/SmartConsole_OLH/EN/Topics-OLH/NZWusyHm6c__hj6NSFa-VQ2.h...
"A rule using a time object applies only to connections that begin during the time object's time frame. If the connection extends past that time frame, it is allowed to continue. The relevant time zone is that of the Security Gateway enforcing the rule."
