It's so awesome that your surgeon is supportive of you continuing to breastfeed. When I had my first consult, my son was 8 months and I was nursing almost exclusively. He told me that he wouldn't do the surgery until I weaned. I'd planned to wait for summer to do the surgery because of school, so I figured at least I'd get to a year. Well, at 10 months my son decided that all he wanted to do with my nipples was chew on them (he had 6 teeth!) and after almost a week of every feeding consisting of using me as a chew toy rather than actually drinking, I cut him off. I wish it hadn't stopped so early/abruptly, but I suppose it was a blessing in disguise since I don't have to worry about weaning for surgery now.
Anyway, blah blah blah. LOL Good for you for sticking with it! I would echo the previous posters who recommended building as big a freezer stash as you can now - that way if your supply does go way down, you'll have milk for him for a while longer.