If you exclusively pump and store, you will need to pump at least once during the night. If you are exclusively breastfeeding, you do not need to pump at night.
If you are doing some combination of breast and bottle feeding, or if you are strictly pumping and bottling, then you will need to wake up at least once during the night to pump. You do not want to go longer than 4 hours between pumpings at night, especially during the first few weeks. As your baby gets older, you may be able to stretch out the pumpings to closer to 6 hours.
If you don’t pump at night, you risk decreasing your milk supply. You also increase your risk of getting plugged ducts and mastitis.
If you find yourself struggling to pump at night, try to pump when you wake up for other reasons such as going to the bathroom. Remember that it is better to have a short pumping session than none at all.
Another tip is to leave the expressed milk in the bottles and tubing after pumping. As long as you either use or refrigerate the milk within 5 hours of pumping, you can wait until morning to clean your pump parts.