Re: 8 years?
"He'll be in office for the next 8 years unless the parties - Democrat, Republican, Libertarian, Green, Commie, whatever - hurry up and find an electable candidate for 2020."
Hmm, better change the constitution then. Getting the job of president isn't enough.
If someone is the type of person who is highly capable and motivated to do some good for the country, standing for president is pretty much the last thing they'd decide to do. Why? Because if they got elected they'd then almost certainly run information the problem of not being able to push hard decisions through congress.
Result - none of the really good people bother to get involved. America's loss.