I find I'm the most full in the morning and can pump at least a bottle's worth (4-5 oz) and still have milk for my baby to nurse on afterward, but that's also because she sleeps through the night so I'm really full! I've been pumping every morning, on days I work and days I don't...both to build supply in the fridge and freezer, and to increase my supply, and it's going great. How much you can get at one pumping depends on how much you produce. I seem to make more milk with my second than I did with my first, and I pump for 20-25 min. one time/day, and get 8-10 oz. in one sitting (usually because I'm so full by then I'm about to burst). I've been back to work for 4 weeks, pumping only one time during the day. I only work 2 days/ week, but I still thought it would take it's toll. It hasn't! The other days she nurses on demand, and I make sure she nurses twice in the morning before we go, once when she gets up and then right before we go to the car. I have a 3 year old as well.