Good to hear he is doing well!
I was told with my first that I needed to wake him at night - no sleeping more than 6 hours. He generally woke, but if he didn't, I woke him.
With my second I just went with the flow a lot more. He never really slept more than 7 hours. Maybe once or twice at that age, and I would wake because of engorgement. So I'd just express and leave him sleeping.
I think if you are confident that your son is catching up during the day - feeding sufficiently , then I think an occasional long sleep would be ok. You might need to express though or you could be very uncomfortable in the morning.