My LO will be 4 weeks old on Tuesday and I got all the advice that you had received, though my LO only would feed 10-20 minutes on one side only. After 3 weeks, his weight is from 6lbs 2.3 oz at birth to 8lbs 1oz at the doctors on Thursday and feeds only every 3 hrs, so clearly, he didn't conform to what he "should be doing". Go with what your LO is wanting. Offer the breast back, if he doesn't want it and seems content for 2 1/2 - 3 hrs, and is gaining weight well, don't worry.