I don't see that you have to go very far into the future to have your efforts negated, because after you die how can you objectify your efforts? If you argue the influence of your efforts live on past your own life, then you have to address two things (at the very least):
1) The law of unintended consequences (are you a Gengis Kahn, a Ghandi, a Walter Mitty?)
2) Return to mean (all things average out over time).
I understand this viewpoint steers towards Defeatism, Absurdism, Existentialism and Nihilism, plus it's cliched to the point of "Dust in the Wind" by Kansas et al, but that does not mean it lacks merit. This viewpoint can further be amplified on by extrapolating a future history, and/or reviewing the extinction of a species, and/or reviewing the negation of a human culture, as well as the individualistic stance I refer to above.
Absurdism is a philosophy stating that the efforts of humanity to find meaning in the universe will ultimately fail because no such meaning exists (at least in relation to humanity). Absurdism is related to Existentialism, though should not be confused with it. Absurdism has its roots in the 19th century Danish philosopher, Søren Kierkegaard. Absurdism as an "ism" was born of the Existentialist movement when the French philosopher and writer Albert Camus broke from that philosophical line of thought and published his manuscript The Myth of Sisyphus. The aftermath of World War II provided the social environment that stimulated absurdist views and allowed for their popular development, especially in the devastated country of France.
Existentialism tends to view human beings as subjects in an indifferent, objective, often ambiguous, and "absurd" universe in which meaning is not provided by the natural order, but rather can be created, however provisionally and unstably, by human beings' actions and interpretations.
Defeatism is acceptance of defeat without struggle. In everyday use, defeatism has negative connotation and is often linked to treason and pessimism, or even a hopeless situation such as a Catch-22. The term is commonly used in the context of war: a soldier can be a defeatist if he or she refuses to fight because he or she thinks that the fight will be lost for sure or that it is not worth fighting for some other reason. The term can also be used in other fields, like politics, sport, psychology and philosophy. The term originates from France during World War I.
Nihilism is a philosophical position which argues that the world, and especially human existence, is without objective meaning, purpose, comprehensible truth, or essential value. Nihilists generally believe all of the following: There is no reasonable proof of the existence of a higher ruler or creator, a "true morality" is unknown, and secular ethics are impossible; therefore, life has no truth, and no action is known to be preferable to any other.