I'd say no, movable Thumaturgy blocks are a bad idea. It's not just about this particular spell itself. Rather, it sets a bad precedent.
If he can use them for blocking sound, why not for blocking physical damage? It's not that difficult to get a huge amount of shifts on Thaumaturgy. This is fine for Wards - they're immobile. However, actual long-lasting physical wards could lead to incredibly overpowered results.
At my most generous, I'd say you might allow it, but use the Time Increments table and start from "instant"(so, if he wants an hour-long shield, that's 7 shifts right there) - the duration of an Evocation block. Even so, it's a bad idea. It allows for any competent spellcaster with a cult(or other manpower willing to contribute consequences to the spell) to have a nigh-impenetrable shield for a very long time(after all, Time Increments go into years and lifetimes).
So, really, this situation would be better handled by the Temporary Power rules. Let him use a Thaumaturgy spell to say he stored the energy of the spell. At the actual scene where he wants to use it, allow for him to pick up Refinement as a temporary power. That's 4 four Enchanted Item slots right there, this gives him plenty of uses of the "item".
So, anyhow, I'd play it like this: base complexity of the spell is equal to Lore(the enchanted item's Strength) +0-7(for a scene long duration, depends on what the "base" time is) +2(1 Refresh being roughly equal to 2 shifts). After the spell is cast, he can spend one Fate Point(Temporary Power rules) in order to gain access to an "Enchanted Item" worth 4 Enchanted Item Slots(ie. -1 Refresh worth of Refinement) for one scene. He can only do this once, afterwards the spell is "spent" and he'd need to cast it again to gain any benefits.
Anyhow, even this feels fairly generous but I guess it's in keeping with the theme that a prepared wizard can be an nightmare.