I think the NEC has adequately provided the guidelines for installing expansion fittings for raceways be it metallic or non metailic. If the building is shifting is one thing but if the temperatures are causing structural materials to expand or contract they have more of an impact on the PVC than the other materials so I would not be concerned with anything except the PVC. The expansion of wood or concrete is nothing in comparision. I would ignore it. It is also possible in most cases to install a raceway system in such a fashion using elbows etc and not have to worry about expansion fittings at all.
