Should let the baby latch as frequent as possible. When the baby latches on, there is signal to the brain that the baby's hungry, and gradually she will start to produce more.

Side track : I used to take 20 minutes for me to clear both breasts, and since 2 months ago I've been using up 6 hours to pump per day (1hour - 2hours per session). Baby is now 13 months old and I'm contemplating to slow down a bit. I'm gradually reducing the pumping time to 20 minutes (whatever amount I can get in 20 minutes without fully emptying the breasts) and the supply has dropped a little. My production peak was 36oz per day whereby I get to freeze 12oz for donation daily - now it's slowly going down to 30 - 33oz per day and I'm having lumpy (.)(.)
I'm hoping that I don't have to mix with formula any time soon. I followed my industrial nurse's advice and I'm tweaking my pumping schedule.
Any experienced mummy here knows how to deal with engorged and lumpy (.)(.)? I really don't want another session of mastitis. On the other hand, I'm not supposed to fully empty the girls as that'll make me produce more. I'm scheduled to pump every 5-5.5 hourly. TIA!