The achievement Gotta Go Fast is winning the game in under 40 turns in Iron man mode.

After completing the game the first run in over 50 nearly 60 days I'm trying to get those last achievements.
Any-one has experience with "Gotta Go Fast"?

My first step in doing that is trying to finish under 40 in regular mode, normal difficulty.
I'm now in day 29 and I'm not sure if I should already try to attack any bosses.
Do they level up with you, as their kingdoms do or are they always as bad-*** as you can get them.