I know a woman who exclusively pumped for her first son, she did that until he was 18 months. Wow, it was a dedication! I think that women who generally have a good supply by nature may successfully pump for a long time and have supply. But, I guess, they need to pump frequently and kind of "on demand" if you kwim. They need to make up for growth spurts and pump then more often. Pumping may become very time consuming but it it is a goal, it can be done.
Generally, if you compare baby nursing action to the pumping action of a pump, baby is much better at it than a pump. Some women can nurse successfully a baby but can't pump more than an ounce of milk.
Some women still have some milk months after they weaned their children, even years. If you worry that a missed feed or two will lead to drying up your milk, well, they will decrease your supply but won't make you dry up completely. It is a much longer precess unless you start skipping feeds frequently and start weaning early in the game before your supply is fully established, before 6 weeks.
