Night advice?

My little guy was waking up every 3-4 hours to feed, and just recently he has slept 6 hours in a row (not consistently) ( some nights he still wakes up every 3 hours) On nights like tonight he went to sleep at 6:30 after I would say roughly 4 oz of milk. I went to bed at 9, and I woke up ready to nurse at 12 because I hadn't nursed since 5:30. So, I am extremely full after over 6 hours. I woke baby up at 1am (by changing his diaper) he nursed on one side for about 12 minutes, but sleepily and then went back to sleep. So, here I am pumping for some relief. I am excited that he is sleeping longer and at night because I miss sleeping more than 2-3 hours at a time. I pump every 3-4 hours at work, nurse when I am home, and supplement with formula when he's still hungry. I typically get 4 oz when I pump for 15 minutes, but the last time he slept for 6 hours and I didn't pump my supply dropped to 3 oz when I pumped the next day. So, I am just wondering how you other nursing/pumping moms deal with the sleeping 6ish hours. Does your supply adjust eventually so I would still get the same during the day or should I be pumping when I wake up engorged? I'm a first time mom and come from a long line of ladies who decided not to breast feed. So, I'm just sort of wondering what works for everyone else. 🙂