Alexandre Erler, in his essay "Is there any point in worrying about the tedium of immortality?," rightly concludes that we should not regard this supposed threat as having "any serious normative implications for the use and development of life extension technologies." Erler writes,

As for those who might share Walsh’s view and enjoy their life more due to the awareness of their own mortality, they might still preserve that benefit by committing themselves not to use life extension technologies when these become widely available. Of course, when the time to kick the bucket seemed near, they might find themselves unable to respect their previous commitment. But they might perhaps protect themselves from such a hazard by writing advance directives stipulating that life extension procedures should not be made available to them. Or if this were not possible, they could at least publicly declare their resolution not to use such procedures, so as to make it embarrassing for themselves if they failed to meet it. However that may be, the risk that some people might prevent themselves, by their own weakness of the will, to die when they would ideally have wanted to, does not seem a sufficient reason to deprive other people of the benefits of a radically extended lifespan. Pace Temkin, I would conjecture that many of us would welcome greater opportunities to learn everything that we find worth learning, to accomplish more things, and to spend more time with our loved ones. Some have also suggested that future humans might become able to experience goods that we cannot even think of today.

Link.