Sometimes I like to pay the full balance manually the moment I receive the statement, particularly if the balance is large. Other times I just leave the DD to be collected as scheduled.
All other CC's I have ever had, when I pay the balance in full manually, they never took the DD (provided of course, I gave them enough time, I believe 3-4 working day before the DD date and the DD is not taken).
What's funny, a couple days after I had paid the full balance manually, the Amex website reflected this, with information that no DD will be collected (while before the manual payment, it displayed DD date and amount

).