I think i've had someone live to 76 or so. The first rulers usually live the longest on average, since they start out in their 20s or 30s (for the rulers most commonly picked), usually without any diseases or wounds to begin with (there is that one inbred, war invalid Italian count of course...). So they get the first couple of decades "free". Plus, if you start with a count, you won't be warring that much in the start.