It is possible to acquire a long-lived token, with an expiration time which is longer than the lifespan of the long-lived token without an error. The documentation states that an error is returned when the timeout is longer than the set lifespan.
Last Published: October 23, 2015ArcGIS for Server
Bug ID Number
October 8, 2015
July 28, 2020
ArcGIS for Server
Operating System Version
The bug has been fixed. See the Version Fixed and Additional Information, if applicable, for more information.