Yes, very important you track your HH account and not just points but certs too. I called the other night to book my last Q3FN and found it was applied to an earlier stay. Turns out they booked two stays with one cert and when it was time for the second (actually first) hotel went to get paid, the cert had been used so they just pulled my last one. No notice at all.

Yes, I should have scoured the confirmations to find out they were reusing an already promised cert, but I do try to give people some credit for being able to do their job right. Guess I was wrong here.