Re: There's always
@TarryB: I give you credit for being able to view this in such a logical way. Your sport analogy is apt, as it would be for any job that requires a level of physical prowess. However, I'm not sure the same is true for jobs that involve knowledge and intellect. If it were the case, then we might be able to also argue that someone who is physically handicapped at any age can't perform as well as someone who is physically well, even if their mental capabilities are equal.
I have trouble separating my emotional response from the facts of running a business, and so my tendency would be to shout: But of course someone at age 56 deserves the same retraining opportunities as someone aged 36!!
It's all a matter of perspective, I suppose.
One other factor to consider here: Typically as a persona ages, the amount of personal responsibility they have increases. They're often caring for children, caring for aging parents, owning a home, etc.
And so, I wonder, is the question about energy of young versus old not so much a matter of older folks not being able to keep up with young energy, but rather a matter of mounting family obligations that make it impossible to have the 24/7 focus on a job that someone in their 20s or 30s offer simply becuase their life is less complicated?