Switch(config-if)# switchport port-security aging {static | time time | type {absolute | inactivity}}
You may not want MAC addresses to be remembered forever
Port security aging can be used to set the amount of time MAC Addresses will be remembered on a port and the 2 options for setting this are:
Absolute - The secure addresses on the port are deleted after the specified aging time
Inactivity - The secure addresses on the port are deleted when inactive for a specified time
Aging of statically configured secure addresses can be enabled or disabled on a per-port basis