They're not irreplaceable. Suitable investments of time and money can lead to an ultimate net gain in time - which is a change over the past state of affairs. If, of course, you choose to take advantage of this. See:
I firmly plan to live to a hundred and fifty or die trying, but I do not believe we're going to see immortality any time soon, therefore I still think that the time we do have is pretty much irreplaceable, especially time in relatively prime physical condition.
http://www.fightaging.org/archives/2008/02/what-is-wealth.ph...
and
http://www.fightaging.org/take-action/