People tend to remember their first and last impression. What’s in the middle is not so important. That’s why it’s good to have polished techniques to exit conversations, so you don’t end up in an uncomfortable situation caused by giving an awkward reason to finish the conversation or just maintaining the conversation for too long.
The best exit is if you have an official reason to do so.
When you are on duty, people will expect that you will not spend more than a few minutes with them.
Another good way to exit is to offer something of value.
You can say, “There is a book that you must read...”, and then exit the conversation. The value can be:
An article, book, or Web site you think might be of use to them.
Someone they ought to meet whom you know and can introduce them to.
An organization you belong to, where you could invite them to speak.
An award you think they should be nominated for.
You can also introduce them to someone in the room.
This will show your goodwill.