You're not going to dry up, but your supply can suffer from regular missed night feedings, especially very early on. If you're desperately in need of sleep, occasionally taking a night off should be fine, but if you plan on making the nighttime bottle a regular thing, pumping that same volume during the day may not cut it. Removing breast milk from the breast at nighttime increases supply during the day. Not removing breast milk at night decreases even daytime supply in a majority of women. Night nursing in the early weeks leaves a permanent impression on the number of prolactin receptors a woman has long-term, and therefore the amount of milk she's capable of producing at 3 months, 6 months, etc. Each woman's body will respond differently, but the majority will have a supply decrease and an unlucky bunch will have a severe supply decrease.