Michael Woolridge may be correct that there is a 4-6 week critical period for
the establishment of the milk supply, but from my experience with my premie I
know that  it is not a hard and fast rule.  I used a hospital grade electric
pump to pump for Katherine born in Sept. '87. I pumped 8 times/day for 30
minutes each pumping. I did try double pumping, but it didn't work well for
me. No greater milk yields or shorter pumping times. My daily totals were
10-15mL a day. A good pumping yielded 5-7 mL. When Katherine actually started
nursing at ~ 3 months, my supply went up. I actually got 10-15 mL  at one
pumping at times. Once Katherine came home at 4 months, I built up my supply
to about 75% using a supplementer. I never tried to totally wean her off
supplement, because of her q4h meds schedule, buts that's another story. So
at least for me in that situation, I was able to increase my supply
dramatically after 6 weeks. I guess that the 6wk cut-off is a good thing to
keep in mind, though we may also want to remember that there are exceptions.

Carol Kelley, LLLL