[OmikronWarrior]

BoT is pretty close to being a game changing spell, and the effects will drastically hit your nation. Don't worry so much about quantifying the spell. Look at your nation and see how it stacks up to other nations to get a sense of whether or not you come out ahead in casting BoT.

For example, human nations with old mages and Abyssia are going to get hit the worst. Blood nations can sometimes mitigate this with Boots of Youth. Most mythical nations will only be partially effected, depending on the ages of units. Undead nations are only inconvenienced while LA Ermor is totally unaffected.