Noah's one and he's been in size 3 for forever (several months). The range is quite big, I believe from 20 to 28 lbs or something like that...so, I expect him to stay here for awhile. I think I go through a case about every 2 weeks? I go through tons of baby wipes, bath products, and lotion. I don't know what brand you are buying but I tried ALL of them. Believe it or not, I like the Target generic the best! And, they are a LOT cheaper :) You could always put your extra funds in a savings account and then buy the diapers as you need them.