I would like to add a piece of information, if I may. What you're saying is true. The actuarial report contains an assumption. Again, it's an average, because the total cost is evaluated using averages. On average, the surviving spouse is three years younger than the plan participant. So yes, the spouse will receive benefits for a slightly longer period of time because of their age, but a scenario like the one you're describing would still be the exception.
On June 18th, 2013. See this statement in context.