My four Grizzly Hills quests, reward in 6 minutes or so...
- 12-14% of a level, with two piece 10% experience heirlooms... at level 73.
- 07-08% of a level, with two piece 10% experience heirlooms... at level 77.

So basically 7-8 days per level initially.
And at this point the Priests/Hunters are looking at 12-13 days per level.
The quests turned green at 77th, they were still yellow at 76th.