To optimize milk production, breasts should be nursed well or pumped to empty about 8 times per day (every 3 hours or so). BEFORE MILK COMES IN AND AS IT'S COMING IN, PUMP 10-15 MINUTES if baby doesn't latch/suckle well, to stimulate milk production hormones.

When pumping How do you know when you're empty?

There's no test or way to know for sure. In general, though, if you gently shake your breasts and they feel mostly soft and you don't feel the heaviness of milk sitting in them, you're probably fine. One thing that does NOT mean your breasts are empty: the milk stops spraying when you pump.

What is a letdown when pumping?

Letdown is the physical process of getting the milk to flow from your breasts. Most importantly, letdown is a conditioned reflex. That means letdown is caused by various triggers, such as nipple stimulation and the hormone oxytocin.