Share 'Couverture Shelf Life'

I have a block of Callebaut 70% dark couverture which shows an expiry date of late Aug 2011.  Also a block of Callebaut 56% dark with the same date.  They have been stored in a cool room in containers.  What's the general rule for using chocolate that is over its  expiry date?  What about others like white and milk chocolate?