Ah, so a medium campaign difficulty sounds about right... I quite enjoy being at peace for a while so hopefully that'll ward off overt AI agression.

In medium vs. very hard battles - do troops tire noticeably faster? Are troops on medium a bunch of never-tiring Lance Armstrongs or do units on very hard collapse before the reach the enemy? How pronounced is that difference?

I figure one could use that advantageously... if you prefer to hunker down and defend your empire, a very hard battle difficulty would work in your favour over time... what with the baddies having to come/run/climb to reach you.