If exclusively pumping then many would suggest every 3hrs 15-20min each. If you're going back to work then listen to your own body. I asked around before I started working and there was sooo many answers ranging from every 2hrs to 4hrs. In the end, I followed my own body. 1st 2 weeks of work i pumped twice at work. Power pumped (20-10-10min) once to increase supply and 20min once a few hrs after. Now I pump whenever I feel like it's full. some days once some days twice :)