After the updated POWER8 firmware, with my commits merged to upstream candidate "next" branch of powerpc-utils's activate_firmware utility last week, and with the ongoing efforts of the Electronic Service Agent team based on my work, it will soon be possible to make the update happen on the fly on provisioning a new update-access-key to the utility.
IBM Power8 customers will also be able to look at the current UAK Expiry date to make a decision as to when to update the system with a new key and verify whether date has been updated after providing the key or not.
Quoting the man page the options added to activate_firmware utility are:
When used with this option, the command either fetches the current Update Access
Key expiry date or sets the Update Access Key expiry date if
The activate_firmware utility will not directly be used by the end user but by an update_flash script to view or extend the firmware entitlement date by providing a new update-access-key.