The nonexistence of a maximal reward juxtaposed with the eternal potential to increase reward by delaying it.

Knowing that you'll never achieve something, and that there's no intrinsic reward from pursuing it, would you still do so? According to this, you would, because of the opportunity cost of not pursuing it. You are maximizing a reward which you'll never acquire.

Assuming: infinite lifetime, nondegeneracy of the reward with age