it depends on the baby and how fast they're growing. these babies can still fit in size 1 but the capacity can't quite keep up with their pee amoun for long period of time. we're using up whatever we have left of the box during the day when we can change them more often. For overnight, we put them in 2s so they can make it through the night. If I can get away with not changing a diaper overnight, that's less work and more sleep. congrats on the baby!!!