Everybody’s different but my milk supply was pretty sensitive when I was away from my babies so if I did not pump every two hours my supply would diminish. With my first child people told me I needed to pump for 10 to15 minutes so that’s what I did. With the second I did not pump for a certain length of time but just until I got the volume I wanted usually 3 to 4 ounces (usually took 5 to 10 minutes). I did have a dedicated lactation room which was super helpful. Good luck!
Reply to Working moms: how often do you pump at work/how long does it take?