Breaking the barrier: Can you get too comfortable in your relationship?

So you've been together for awhile.  The honeymoon is over and you are getting quite comfortable in your relationship.

Can you get a little too comfy?  I mean...should some stuff remain a mystery...Like the fact that you can belch out the National Anthem.  Or that you flip your draws inside out and wear 'em again (fellas....)?

Or that you wear granny draws?

How comfortable is TOOOOOOOOO comfortable?  What things do you do when you are good and settled in your relationship, that you did not do when you were just kickin' it or dating?