Alan should know better
The spell description is old and poorly worded. The prosperity bonus ends when the spell ends.
Good Point. Sometimes even I get confused by the descriptions.
I have a new general rule though...
If the spell helps you, then its bonuses are temporary, if the spell harms you then usually it is permenant.
It is easier to tear things down then build them up afterall.
What do you think, B?
Sound about right thematically?