Mechanically, there's no reason thaumaturgy can't create long term blocks as long as it adheres to the two inherent limitations - casting time and symbols. The symbol requirement probably does mean such blocks need to be tied to items.
For game play purposes, I ask players to pay for any long term powers with refresh. It can be justified by thaumaturgy, but they'll still need to spend refresh on that "Toughness" spell (or other result).