How I teach it to my employees is this, if you have a good reason to be gone, then do it. Otherwise, you should be here. We request only one long extended absence per year (greater than one week) and remind them that they are part of a team. I've only had one employee I have needed to talk to about taking too much, and he knew it and is no longer here because he was doing a side project and couldn't devote enough time here.