You can delete the license from your device but the clock will keep counting.
Information on grace periods can be found here, with examples:
https://www.paloaltonetworks.com/services/support/support-policies/grace-period
The support license, for example, has a 30-day grace period:
If a hardware platform is shipped on January 1, 2011, then the start date for support will actually be January 31, 2011 (30 days after initial ship date), or earlier if the hardware device was activated before January 31, 2011.
Now that Transporter's question was answered, please allow me to expand on this common question about showing the licenses installed, and deactivating licenses via the CLI.
The CLI command to show which licenses are currently installed is:
> request license info
Current GMT Date: July 18, 2016
License entry:
Feature: WildFire License
Description: WildFire signature feed, integrated WildFire logs, WildFire API
Serial: 0009C10xxxx
Issued: March 26, 2015
Expires: September 04, 2017
Expired?: no
License entry:
Feature: Threat Prevention
Description: Antivirus, anti-spyware, vulnerability protection
Serial: 0009C10xxxx
Issued: March 26, 2015
Expires: September 04, 2017
Expired?: no
License entry:
Feature: PAN-DB URL Filtering
Description: Palo Alto Networks URL Filtering License
Serial: 0009C10xxxx
Issued: March 26, 2015
Expires: September 04, 2017
Expired?: no
<results trucated>
In fact, there are more options for licenses in the CLI: deactivate, fetch, info, and install.
> request license
> deactivate deactivate licenses
> fetch Get new license(s) using an authentication code
> info Show information about owned license(s)
> install Install a license key
If there is a specific license that you want to deactivate, you can use the following command to list the current license keys installed:
> request license deactivate key features
[ Start a list of values.
AutoFocus_Device_License_2016_04_26_S1782944.key 2016/04/27 01:17:11 0.3K
AutoFocus_Device_License_2016_06_15_S4740206.key 2016/06/16 01:13:24 0.3K
GlobalProtect_Gateway_2015_03_26.key 2015/10/12 05:43:59 0.3K
PAN_DB_URL_Filtering_2015_03_26.key 2015/10/12 05:43:59 0.3K
Threat_Prevention_2015_03_26.key 2015/10/12 05:43:59 0.3K
WildFire_License_2015_03_26.key 2015/10/12 05:43:59 0.3K
<value> member value
Then continue with that same command to deactivate a specific license key, say the last WildFire license.
> request license deactivate key features WildFire_License_2015_03_26.key
Another command that can come in handy is to show which support license the unit has installed on it. This information can be found by typing in the following command:
> request support info
Support Home
https://support.paloaltonetworks.com
Manage Cases
https://support.paloaltonetworks.com/pa-portal/index.php?option=com_pan&task=viewcases&Itemid=
100
866-898-9087
support@paloaltonetworks.com
September 04, 2017
Standard
10 x 5 phone support; repair and replace hardware service
This command is very helpful to show not only the level of support this device has, which is Standard Support, but that it expires on the unit in September 2017.