sorry Third spearman from the left, i was fooling about! oldest ruler i've ever had was an 83 year old Egytian Caliph, great stats and still leading armies from the comfort of his wheelchair!
i currently have a 54 year old Welsh king whose ONLY V&V is Magnificent Builder...he's been around for ages, but i've carefully protected him and not let him do anything naughty, hence the lack of any other traits. his heir is now about 49, and he had two older sons who were not very talented and whose hunting parties and scouting expeditions were sadly and unfortunately <ahem> 'betrayed' to the Saxons by some nefarious b*stard (er, me)...
i agree though, possible (serious) vice and virtues for increasingly aged rulers would be good, reflecting either an experienced statesman or a decrepit and dribbling loon with a long white beard. maybe you could institute a regency if the king got too gaa-gaa? historical precedents abound...i'd also like to have seen regencies if the heir is too young, although this usually led to civil war and much skullduggery.
maybe teching up to things like 'Physician's Guild' or 'The Discovery of Plumbing' should result in increased lifespan for generals and rulers? or maybe not, in the case of medieval plumbing, which was made of lead...!