I was going to post about this, but found this old thread.
One of my boys licks a ridiculous amount. Just Henry as he is really really placid. If you put a finger in the cage, he will come rushing over to lick it, just as he would if it were food.
When he's out being stroked, it is hard not to get a licking. You have to approach him from behind, because if he sees your hand coming he will lift his head up to get you. I moved my arm away once and he just carried on licking my t-shirt.
Once going, he can literally not stop for a whole episode of Eastenders.
He MUST be getting something off me. :red