What I do with long term achievements: to do it, do it and in doubt, use the workshop rules.
I want to get +1fortune.
-Cool! How?
-Dunno, maybe build a church or something, to attract people and tell everyone we're here to stay.
-Cool! But first you're gonna need the approval of someone close to Uncle, Balls maybe, or the gang will fuck your shits up. Plus, that's gonna take you some manpower and a few weeks to do it.