Fish? Cut bait? Play with worms?

So, I have been thinking... When does one give up on someone in the Internet world? When does conversation move from potential to pen-pal-tial? (Yes, I will hit myself for typing the last sentence. But, really, I am not on this site to get email buddies.) I dunno. I am not at that point yet with my chat-buddies, but I could see the issue possibly looming in the distance.