Maybe slightly longer than that, but it depends on how hard you run 'em. Besides they aren't really refueled anymore since that would involve cutting into the pressure hull. They just de-fuel and scrap them when the reactor cores wind down.
Had better hope we don't run into a situation where we could have brought a bunch of ships out of retirement, because we need every one that we can get our hands on. That's no worry though, since it isn't 1912.....