How long will a mob chase you after you enter combat with it? How far will it chase you? Will attacking the mob during chase completely reset the time / distance that it will chase you?
This, as has been pointed out, varies wildly, but generally, in the overworld, mobs can be kited for any amount of time, but if you move too far from where you entered combat, they'll snap back.
In dungeons, mobs will generally follow you until you or they die, although there are exceptions (besides the obvious, such as bosses).
Of course, occasionally strange cases have appeared, and mobs have been known to be kited from the Blasted Lands to Stormwind…