Hi KiwiPanda what's RL? Oh, I get it, Real Life?!?
Ok, when I went back to work (only 2 days a week though) in September, I did nothing to prepare. I worked 3 days, then had the summer holidays off, and that was a useful trial. I left a fair amount of EBM in the freezer, mainly in 3oz portions. I found at the beginning that I had to express as the boobs were painful, but as time went on they adapted. however, I am happy for BB to have formula to make up the extra as I am unable to express enough for his two daytime feeds due to my job being very hectic. If you have an electric pump and a sympathetic or flexible working environment, I'm sure things would be different. The other thing BB did at the start was upped his night feeds to compensate for losing out in the day. A pain in terms of sleep for me, but at least I knew he was getting the good stuff.
So I guess my answer is don't worry too much about not being prepared. I don't think you can be, as you don't know how your baby and your boobs will react. I found that both were remarkably adaptable. In terms of how much milk to leave, I used to defrost maybe 6oz and then MIL would defrost more if needed. On one of the three days I first went back, BB refused all milk and my EBM had to be thrown He had a mammoth feed when I got home. In the early days, I would express some at work and some at home, and then leave that for the next day.
Hope that helps. When I first went back, it was very tough and emotional, but now we have both settled in, it's great. BB absolutely loves his time with his grandma and I now really appreciate the time we have together. Plus it is good to have my own money coming in. Sunday nights are still bloody awful though as I can't bear the thought of leaving him
On a separate note, I am starting to worry about how I am ever going to stop BFing!! BB seems to be living on thin air and breast milk at the moment, and turned 11 months today. He is teething, so I know that's a factor. I even tried today to give him some (warmed) EBM I had knocking around in the fridge in a beaker and he pushed it away after a taste. Only fresh will do from me it seems!