I've been pumping for 5.5 months.
1) For the first 2 months I pumped 8x a day and got about 45 oz. When I went down to 7X it went up to about 52 oz. At 3 months I dropped another pump and it stayed the same. At 4 months I went down to 5x a day and took a 10 oz. hit so I currently pump 38-40 oz. a day.
2) I personally didn't notice a big increase at 12 weeks. Just a gradual increase until I peeked at 52 oz. I'm sure if I was still pumping 7x a day I would still be producing that much.
Hope this helps!