The general recommendation for how often to pump breast milk depends on the situation:

• For newborn babies or to establish and maintain milk supply, it is ideal to pump every 2 to 3 hours, including at night, roughly 8 to 12 times per day. Pumping this frequently mimics a newborn's feeding schedule and helps maintain milk production.
• If returning to work or supplementing breastfeeding, pumping every 3 to 4 hours during the day is typical to ensure enough milk supply.
• Exclusive pumpers (those not breastfeeding directly) often pump every 2 to 4 hours, including night sessions to keep milk supply steady.
• Pumping sessions generally last about 15 to 20 minutes or until milk flow slows.
• It's important to maintain a regular schedule based on individual needs and to adjust according to milk supply and baby's feeding cues.
• For personalized advice or difficulties, consulting a lactation specialist is recommended.

In summary, pumping roughly every 2-4 hours depending on your situation, aiming for 8-12 times in 24 hours initially, is the common guideline to maintain or build milk supply.