In this question, the user asks the better way to close sessions because he was having some errors.
The most voted answer is Ayende's answer that says:
You should always use session.Dispose(); The other are for very strange occurances
Should I really always call session.Dispose()? Isn't enough to call session.Close()?
Session Dispose() does a couple more things than just Close()ing, so yes, always use Dispose()