Should I stay or should I go now?

So I am almost level 76 and I still haven't quested anywhere other than Borean Tundra, Howling Fjord, and Dragonblight (which seems like it has the most quests I've ever seen in a single zone). Dragonblight is definitely beneath me now but I am having a hard time leaving the zone due to wanting to finish all of the excellent quest lines. The question I guess is: When is it time to move on to the next zone?

If I use the achievement for quests completed in a zone as my ruler for when I am "done" with a zone I'll be 80 before I finish the Grizzly Hills I think. On the other hand if I just use my level to determine which zone I should be in I would be missing out on all of the excellent quest chains (and the nice rewards that usually come at the end of these chains) and story lines I've been running into in each zone.

I guess I could always just come back later and finish off the questing in the zones. /sigh

When do you "move on"?