Why are you pumping overnight? Are you trying to build up your supply, or is it so that you can store some milk?
Essentially, your body will adapt to what your babies need, so if they are not nursing overnight (and you stop pumping) then your breasts will produce less milk overnight and the uncomfortable feeling will get better. You will have enough milk to feed them in the morning, if that is what you are concerned about - as I said, your body adapts, so it will adjust depending on when you are feeding.