Thank you for the question. It's one that I'm not perhaps prepared to give you a fulsome answer to.
You're quite right that, in the broader sense, this is based on actuarial assessments. That means you will have some individuals who will draw five years of the pension benefits they have worked their entire career for. Equally, you may have someone who in fact receives a pension for over 40 years because they happen to have that longevity. It is all calculated on the basis of trying to achieve the best investment, so that the funds will be there to try to ensure you continue to receive your benefits, whether you are short-lived or long-lived.
I'm not sure whether that gives you a satisfactory answer. Perhaps this might be one that, because it applies to all the plans, Treasury Board might be better placed to answer.