I've been very fortunate to have a great supply so far and started pumping when I got engorged when DD was about 4 days old.
Loss #1 (missed miscarriage) 14 weeks
Loss #2 (missed miscarriage) 10 weeks
Loss #3 (chemical pregnancy)
Loss #4 (chemical pregnancy)
Loss #5 (chemical pregnancy)
I started right away. When I was nursing (I'm pumping now) I would always pump a little bit after each feeding to increase my supply to more than he needed. Now that I am pumping I try to put away 5 ounces a day.
Re: Pumping stash before going back to work