This is all good info, but I would say you don't need a "stash" before returning to work. SO many times, on here and IRL, I've seen people get so stressed when their baby is just days old about pumping for their freezer. And when you're on maternity leave your baby is so little s/he is nursing so much the last thing you want to do is work pumping into it!
For my first I was like this and tried to pump all the time and put milk in the freezer. For my second I just started pumping a few weeks before I went back to work to have enough for the first few days. After that, I just pumped for what I needed for the next day and kept a little in the freezer for emergencies (maybe 20 oz.?) Both of these approaches lead to the same end result: exclusively breastfeeding for 12 months. The only difference was the stress and pressure I put on myself the first time around.