we ordered them around 24 weeks...and they said 4-6 weeks for delivery too. ?i figured even if the babies came early (which they did) they'd be in the hospital for a while, so it was ok.
We went to order our from BRU at around 25 Weeks and they had them in stock so we took them with us, but I think you should be fine with ordering them when you want to.
Re: When did you order cribs?
We ordered ours around week 25 and it took 4 weeks for them to come in.
Kerri