I work 3 days/week and pump 3x/day. I have a Medela PISA. I used it for about 5 months with DD2 and plan on using it for about 9 months with DD2. Then, I have agreed to let my sister use it. Will I need to get another one if I have DC3? Will it last through 4 babies? I can't really see how I could not let my sister borrow it (they are not in the best financial situation right now.)