I've got a "mature" village with all puzzles solved and all techs bought. When a villager turns 14, they start out on the skill they naturally have (usually either research or farming). As soon as they Master that, I switch them to the other. Once they have mastered both of those, I set them to parenting and let them go.

Most of them reach Master Parent - but even if they don't, they at least have enjoy life and it makes for a lot of fun watching the crowds around the love shack!

If they do get to the Triple Master, I uncheck the "favourite" box and let them do whatever they want. At the moment, my youngest would-be-Elder-if-I-didn't-already-have-50 is 37.