I struggled with milk production with my first 3, and switched to formula at 6 months with them.
My last 4, I was determined to exclusively breastfeed. I drank lots of liquids, took fenugreek, ate oatmeal, and used (LOL) my encapsulated placenta (for the last 2), and was able to successfully breastfeed them until 15-18 months old. Weaning a month before the next was born (mainly because I don't produce enough milk for two).
How long did you nurse your babies?