Two points here:
Is Hiltonguy saying that after I cancel a cert ( not talking a reservation here) and the points have been redeposited in my account that the cert may be still valid???
Which then comes to the next. It is no longer necessary to mail an award cert into to HH to get your points back. Just call in give them the number and it will be cancelled immediately and the points will show up in your account within seconds.
mike