She is just a hair older than Reagan was when he was elected for the first time, and he served two terms. On the other hand, history suggests he may have been well into senile dementia in his second term, so it's hardly a resounding endorsement for the idea of an 84-88 year old President. My sense is that her inclination to run again would depend on who else is evident on the landscape of potential candidates for both parties, and what she sees as her likelihood of winning re-election. I could conceive of her electing not to run in favor of a younger, more appealing Democrat if she felt that was necessary for the party to hold the White House. Other things being equal, though, she, like every other President, seems pretty power-hungry, so it would probably take some convincing to dissuade her from running again.