Hi Mrs. R!!
I'm happy you asked this question and if you don't mind I'm going to give you a detailed answer just in case there's a mother out there lurking who wants to know too.
According to research that has been done by Peter Hartmann, Ph.D in Australia, it' s the frequency of breast emptying that increases milk supply, not the duration.
We usually advise moms without an established milk supply to follow the pumping instructions in the appendix to the guide to the protocols found here:
http://www.asklenore.info/breastfeeding/induced_lactation/gn_protocols.html which is essentially on this page:
http://www.asklenore.info/breastfeeding/induced_lactation/pumping_instructions.html The whole thing shouldn't take more than about 1/2 hour. In the middle of the night, it's sufficient to hand express, or use a manual pump if you don't want to set up your breast pump. If you have a bathroom near your bedroom, just go in there and express until you've basically emptied your breasts (about 5 min each side) and put your expressed milk in a cooler with an ice pack. It will keep until you get up in the morning and transfer it to the freezer or use if for you baby.
The reason for the quick emptying in the middle of the night is to get rid of the little whey protein that sits in the milk acting like a feedback mechanism. It it's there, your breasts think there's enough milk. So we need you to drain it out with the milk. The regular pumping sessions include time for breast stimulation to further increase milk supply. In the middle of the night you basically want to drain your breasts, store what you get and go back to sleep. The middle of the night session also takes advantage of your natural prolactin increase between 1 AM and 5 AM.
If you are interested in reading Dr. Hartmann's article in which he discusses breast capacity and breast emptying you can find it here:
http://biochem.uwa.edu.au/PEH/PEHRes.html It's very interesting but technical so if you don't want to wade through it, just scroll down to the section on "principle findings" for the summary.
Hope this helps. fondly,
