I just did babybacks yesterday as well (or loin backs I should say).
I intended to go 3-2-1, but ended up more like 3-1.5-.5.
Avg temps were 225-250. After 3 hours, I pulled, foiled (with parkay, honey, tiger sauce, and some turbinado sugar).
I decided when I foiled to cut it shorter, because I alread had a good deal of pull back on 2 of the racks, and on the other, it seemed like I had a bone or 2 peeking thru the top (meat side).
When they came off, the were definitely fall off the bone, but not mush, but I can definitely see how going the full 3-2-1 would have really killed them.
'00 Weber Genesis Silver B // '12 WSM 22.5"