[Nagot Gick Fel]

Cainehill said:
Otherwise, let's say someone has invested into 40 fever fetishes, on 20 revenants, and she only has one mage capable of casting black servant / revenant. Now she's screwed - only getting half the income from the fetishes, and not able to remedy the situation for 20 turns, summoning a new undead each turn.

Screwed... for 20 turns? 2-4 turns is a more likely figure. Revenants know how to summon too, don't they? And scouts can be recruited almost everywhere.