If you want me to do something for you and I say I will, I will ask you to give me a deadline. Once I have the deadline, I will do my best (and will usually succeed) to deliver what I promised by said deadline.
BY SAID DEADLINE. This means not much before the deadline. Actually, it often means exactly on the day of the deadline.
DO NOT pester me twice a week within the three weeks preceding the deadline. This annoyance will not make me work faster (I am already working as fast as I can, trust me) or help me prioritize what you need over other things. It will just make me even more pissed, and I am always plenty pissed to begin with.
If I am late, then by all means remind me that I am late.
But if you really wanted your stuff three weeks earlier, then you should have made that your deadline. Otherwise, bugger off and don’t bother me until the deadline.