... And what was the approx weight the diapers were supposed to fit up to?

I am using AppleCheeks which is a two size system. DD is 4 months old and I just switched her out of the size 1s to the size 2s. I probably could have kept her in the size 1s a bit longer, but the size 2s (while huge on her now) fit nicer. I'm not 100% sure what DD weighs right now (I'll find out on Thursday when she is weighed at her 4 month appointment) but I'd guess approx 16-18 lbs comparing her to other babies I know. The size 1s are supposed to last to approx 18lbs so I think she is probably right in line with that.

My sister (who is using disposable diapers) doesn't believe me that these size 2s are supposed to last until my baby is toilet learned. The size 2 AppleCheeks are supposed to fit up until 35lbs which from what I understand us approximately a 2.5-3 year old child.

AppleCheeks did just recently add a size 3 to their lineup but it's advertised for much older kids (3+). I'm assuming parents got by just fine on their two sizes before?