The weight range says 16 to 28 pounds. DD has managed to stay in diapers up to the upper limit in previous sizes.
She has spent about 6 weeks in each size (NB, size 1, and has been in size 2 for 6 weeks or so).
I found a good deal on Amazon for some overnight diapers that work really well. The problem is that I'll end up with 240 size 3 overnight diapers. At 1 to 2 overnight diapers per day, she'd take 4 to 8 months to use them up!
If all goes well with the current pregnancy and we end up with a #2 in 8 months, then it would not be a big deal to hold on to the excess diapers for #2. However, size 3 diapers need to fit for several months for this plan to make sense.
So, how long was your LO in size 3 diapers? 
Re: How long in size 3 diapers?
I'll throw in the next question too--
How long was your little one in size 4?
Thanks! Both of your answers are very helpful. I use overnight diapers for long out of the house trips, so they do get used up a little more quickly than if they were just using them at night.
It appears that it will be safe to order the giant pack of diapers. It is actually for 12 packs of 20 diapers, so I can give excess unopened packs as gifts or donations. These diapers have kept in big messes like no other diaper (at least so far).
If the rest of the pack works as well as the first few diapers, I'll order the 240 diapers from Amazon.
B&W Photo by Wildhouse Photography
Hmm...DD is almost 16 pounds already. Maybe I'd better not jump on the diaper deal. A deal is only a deal if you can actually use the item.
I could just have a heavy wetter on my hands too - which is a strong possibility...
B&W Photo by Wildhouse Photography