The extremely easy way to complete the quest with the 20 minute reward is as follows
Accept the troll patrol quest. Go take and do all of the tasks except for the apocrathy one. DO NOT TURN ANY IN
With the three tasks complete and ready to turn in, abandon the the main quest, "Troll Patrol" and pick it back up again.
This will restart the reward timer.
(if you pick up the apocrathy quest, you cannot pick up the main quest after you abandon it, unless you abandon it also)
Now you can just do the apocrathy part at leisure and then turn in the rest, and bam. Finished with at least 10 minutes left on the buff (ive gotten it down to 15 minutes extra)
there was another one like this but it involved logging out so i posted this one