Limitations of spell casting during a day (or month, and so)

It is basically transforming mythic Europe, and if that is wat you want for your campaign, go for it, just understand that producing a single produce ad infinitum will simply devalue that commodity in the local market. That in turn may have ripples- if Marlin the Mad creates thousands of pieces of furniture by growing trees and shaping them without vis, the value of furniture in the village will drop. When traders come to trade with the village they will buy some furniture in exchange for other goods, because there is literally warehouses filled with locally worthless mass produced furniture. Presumably Marlin stops at some point, and his furniture is being sold further and further away, as the discounts abroad increase and furniture makers across the country curse his name, but eventually the economy will absorb what he has made, furniture will break, and people will begin to learn the craft of making furniture again. Aside from furniture becoming worthless in the local village however, none of this will happen quickly.
Now if dozens of magi start to act like this, with different goods, andbuilding a trade infrastructure, then Mythic Europe is transformed...