I do the same as far as deselecting a particular path, but if they are stressing out at say, farming or any other former path, if they DON'T like being deselected, I put them on "Healing" without training ... and in a lot of cases, that keeps their health bar up to maximum. If that doesn't work, I make a healing stew and dose everyone starting with the elderly who have less than a full health bar, and working my way back as far as the stew lasts, all the way to the children. Keeping the villagers happy at what they are doing also seems to help longevity.
My oldest was 97, but I never got to see him/her at that age so I don't know who that was

... it happened while I was away and the villager passed before I had a chance to actively play the game. While I am actively interacting with the game I see 78 year olds quite frequently. I DO however, always keep my time at 1/2 ... a slower easier pace ... no real need to go faster otherwise, and the elderly don't move very fast ANYWAYS!!
That help any?