Astarion pulls up and off for a moment just to smile and remark -

"If I'm here all night, I'm really not doing that good a job, am I?"

- and then goes back down. He strokes his shaft with one hand in firm pumps as he concentrates his lips and tongue around the tip. Deepthroating is all well and good for a brief party trick, but it's not as useful in getting a man off, in his experience.