So, we only use disposables for nighttime and travel. Sweet P is 16.5 lbs so I just bought a giant box of Luvs size 3 because they say 16-28 lbs on them. However I'm feeling like I can't imagine them lasting that much longer! I'm wondering if maybe I should return the huge box to Amazon and get size 4? If you had a LO and used Luvs how big were they when you stopped using size 3 and moved to size 4?