A while back I spent a few months making a really nice sculpture of a hand out of crayola air dry clay. It worked fine, took details fine and barely cracked when drying. The problem arose in the fingers. Early in the sculpt I took five ovals, etched the contact areas, wet them and stuck them on to the main body. The fingers would occasionally fall off when the sculpture got too wet, but it wasn't much a problem until much later when the fingers simply wouldn't stick anymore. Not even wooden bones could keep the thing together. Eventually I had to scrap the whole thing.
So my question is, was that a problem of cheap clay wearing out over time, or is there some kind of technique for keeping the clay alive longer? Do you have any recommendations for good air dry clay? And do you have any advice on modelling techniques?