I've wondered the same thing about expressing when you have a short time between feeds - DD1 was a four hourly feeder so expressing at the 1 1/2 - 2 hour mark worked fine. But DD2 is more like 2/12 - 3 hours, I haven't tried it yet but to me it does seem like it will be trickier to get it all done with enough time to build up for the next feed. I have thought perhaps when the need arises to express I would either express overnight (when she has a longer stretch) or express at about the 1 1/2 hour mark, then feed her again normally when she next demands it. If she is satisfied with that feed then woo hoo, some EBM to put in the freezer, and I've added an extra 'feed' that my body feels it needs to supply milk for. If she isn't satisfied I could give some of the EBM back to her, but hopefully there would be some EBM left that I could slowly collect up, and it would also be putting that little bit extra demand in there that should result in more milk being produced after a few days. Does that make sense?