Its totally up to you. I started weaning from the pump before I stopped bfing. I just dropped one session at a time over the course of maybe six weeks and we supplemented with formula. I didn't have any problems with engorgement that way. But if you want to pump up until you stop bfing, you can do that too. Its whatever you are comfortable with.
I started weaning from the pump with A around 11 months and was fully weaned off it by 12 months. We also started her on whole milk at 11.5 months so I didn't need the BM during the day. I would drop one session per week and give my body time to adjust before I dropped the next one. That worked well. I didn't have any issues until I fully weaned at 13 months.
Re: Weaning from the pump