With DS I would pump after feedings and store the milk in the freezer. It wasn't even so much to build a back-to-work stockpile but to give me some engorgement relief. Starting about 5-6 days PP I had crazy milk, like two bowling balls strapped to my chest

and so I thought why not pump off the extra to be more comfortable. I didn't really realize that I was actually encouraging a lot of extra production but it turned out to be a good thing. I could get about 4-6 oz after a full feeding for the first 3 weeks or so, and when I started back to work at 9 weeks PP I had 80 oz in the freezer waiting to go. It REALLY helped when the inevitable supply shock hit during stressful work days, so I would highly recommend pumping after feedings to build up a reserve. I plan on doing the same thing this time provided the milk is plentiful early on again.
Still you have to pump regular at work to keep up supply but it was nice to be able to mix in some frozen milk when I couldn't pump enough, this was a big problem around 8-9 months. I would be sure to rotate out the frozen milk before it goes bad, 3 months or so and then replace it with the fresh milk when there was extra. Because of the stash we never needed to give him any formula just mom's good stuff
