What would be cool is another column containing the number of months after which it makes no economic sense to stay with on-demand pricing, even if you never us

What would be cool is another column containing the number of months after which it makes no economic sense to stay with on-demand pricing, even if you never use the instance after that point. In other words, "if you're going to use this instance for at least 4 more months, you might as well get a reserved instance".