What do you think about my strategy of making my customers go away by saying have a good night?
I'm not sure why you would do that. Why do you want the customers to leave?
I don't want to deal with them anymore.
Trying to force customers to leave before they're ready is not an appropriate thing to do. You're supposed to try to help customers and make them feel welcome, not try to rush them out the door.
Why should I care if they stay?
You should care because helping customers is part of your job, so if you continue to hurry them out the door you might get fired. You should think about what your customers want.