I don't pump frequently, but do try to pump regularly and consistently.
I have grad school classes three nights a week, and on those nights, my husband bottle-feeds pumped milk for the feeding I miss while at school. Other than that, we don't bottle-feed. I am trying to pump daily, whether I have class that day or not, to try to get ahead and have a supply available, and just for the consistency with my supply. I know mornings are the best time for me to pump, supply, wise. I tend to pump after his first-thing-in-the-morning feeding, which is usually between 7 and 8 a.m. I wait about 45 minutes after the feeding before pumping.
My observation is that despite pumping the same time of day, consistently after a breastfeeding, the amount I pump in a given session is ALL over the map. Yesterday, I pumped 6 oz. in one sitting. The day before that, about two oz. Today, I got barely three oz. Probably tomorrow will be back up to a full bottle. I'm wondering what accounts for the difference? My son nurses for a consistent time period (10-15 minutes per side), is on a consistent, regular feeding schedule in general, and I am consistently pumping the same time of day (double electric pump, Medela PISA). I have a hands-free Simplicity pumping setup that allows me to massage for higher output, but the amount is still all over the place. All other things being equal, I'm wondering what goes into pumping half the volume I did the day before from one day to the next. What different things could be contributing to this, and what can I do to maximize the output? I really don't want to be pumping multiple times a day between feedings if I don't need to. Just wondering why some days, my cup runneth over, others, not so much, when I'm not really changing anything.
Re: Variables in pumping
I would say your best bet is to add another pump into your day - not only will it get you prepped for when you are not around but it just may increase your supply.
And as usual for all of us- stay hydrated!