I actually don't use the free time quests that much. I used to, using them to level up my heroes and the like ... until I learned that you have to start a new kingdom for each ambition, you don't carry the same kingdom throughout. After that, it's sort of like, what's the point? I honestly never thought to use it to gain achievements, but it makes a lot of sense -- especially some achievements, like the one where your entire town is of the Jacobian faith, that I would never do in an actual game.