Why add vanilla extract after removal from the heat, and what about fake vanilla extract?
Liquid vanilla extract has alcohol in it, so if you add this extract to hot cocoa, puddings, fudge, or anything you make with heat, the alcohol burns off and so does most of the flavor.  If you wait for it to cool off the flavor stays strong.  Same thing goes for artificial vanilla also because of the alcohol levels (but the flavor is just not there to begin with with artificial flavor).  If you use vanilla beans, open up the pod and scrape the inside of it and put it in the beginning with the hot mix.  That is another story.  It is very delicious, but you see teeny tiny little beans swimming in your lighter mixes like vanilla bean ice cream.