One thing that really seems to help is to make sure that your villagers have plenty of food, a bunch of farmers, several trained doctors, then leave the game off for several days. More often than not, you'll turn the game on and find that you have had several villagers live beyond the age of 90. Don't do this if you're not willing to have villagers die, though. When I've done this, there have been only deaths from old age, since my village was healthy and well established, and I was just going for the Ancient Elder award.