The 15 minute question

Do you know people that you need to be diplomatic about talking to, time wise, because you know that you might get stuck talking to them?
That just happened to me.
I went into one of my supervisors' offices to ask a single word answer type of question, and it turned into a 15 minute conversation. This person loves to tell me what he knows, and so, he answered the question, and kept going, and going, and going. I actually attempted to end the conversation about 5 times. I got out the door at least 3 times, where my back was to him, and he kept talking, so I had to turn around and walk back in his office.
It was painful. I make it a point to never talk to him close to 4pm, the time when I go home each night. This guy is the same guy who gets in real early each day. I'm talking 6am early, and he loves to comment on what time he gets in, just to make sure we all know.
He also makes it a point to round the floor to see what time we are all getting in. I know, it's lame. Ah, but what can you do. Releatively speaking, I come and go as I please, and answer to no one, so I can't complain.