|Many people have 4-6 covers in each size. I had 6 covers in each size, but found that although BF poo was more likely to get on the covers (not often, but given its nature . . .), it's easy to handwash off with some soap, and newborn pee is pretty mild stuff, too, so I mostly hand-washed (or just rinsed) my covers for about the first year (I'd put them in the wash sometimes, just saying I didn't feel like they needed to be machine-washed every time). When my boys were older and their pee was stronger, I felt like the covers needed more cleaning. That's when I found I liked having more covers, so I didn't have to worry about getting them through the wash. If I were to do it again, I'd probably have four (or fewer) covers for the S and M (I didn't use XS/NB, but would apply the same reasoning) and at least six for the L (I ended up with eight, and that's a pretty happy number for me, and works out well, esp. as L is a size that's usually worn for a much longer time than the others).