I'd probably leave the energy variable completely out of the equation. Motivation and focus are probably more relevant to the question at hand and it's not difficult to find 'old' people who at the very least 'appear' to have more energy than most young people (but perhaps they are simply using the energy that they do have more wisely).

Likewise, any advantages of age are going to come with the individual and not the year said individual was born.

Full Disclosure: I'm neither old (depending on your definition I suppose) nor an entrepreneur (again...).