It depends a lot on where you live. In the Southwest residents learn fairly quickly that all stucco cracks. It is the nature of stucco as it is faux block. Differences in the material used, the underlying foundation of the structure and the surface to which the stucco is applied all affect its stability as do the thickness of the application and quality of the material used to prepare the stucco are all reasons and causes for the cracks. If you live in an earthquake zone this can also obviously affect the stucco and it's durability. The rule of thumb as taught in the area I live is that stucco cracks, you patch, it will crack again! That is the nature of stucco. If the stucco is applied to solid block it will be more durable than if applied to chicken wire, the stability lies in part on the surface to which the stucco is applied not taking into consideration the area where you live, it's geological issues and other foundation settling worries.
I believe your problem lies with the stucco contractor. as you say the home is new and unless your home is situated upon a sinkhole you should not have that much settling in a new home.