Problem 1: The Permanence Assertion
The first problem is that argument is built on an assertion. The assertion is that an experience has to be permanent for it to have meaning. The assertion is never proven, it is obstinately accepted by fiat by the theist. Yet, I know that holding my daughter the moment she was born, was an extremely meaningful experience. It still provokes a powerful reaction in me. That eventually I'll be dead, does not alter the fact that I felt something real, that it did have meaning for me. It doesn't have to be a permanent experience to have meaning.
If I don't have the belief that permanence is a prerequisite for meaning, it's not enough to keep repeating that assertion. You need to produce a strong argument, not insults, to establish it. I've never heard such an argument.
Problem 2: An eternal afterlife makes this life meaningless
This can be established by comparing the different outcomes under different assumptions about an afterlife.
Lets suppose however, that each experience in Heaven gives a payoff of B, you average an annual level of happiness of b when you're alive in the mortal realm, and that each torment in Hell gives you a payoff of -H. With Heaven being superior to this life, and Hell being worse, let's simply say the B > b > -H.
Both Heaven and Hell are eternal, and thus provide you with an infinite benefit (or harm) stream.
Hence the actual payoff to being in heaven is ∞B and the payoff to being in hell is ∞(-H). With these being infinite streams, then the B and and -H is not really relevant. Heaven has an infinitely positive good payoff, Hell an infinitely negative payoff. This is largely the logic behind Pascal's Wager. In that wager doesn't matter how unlikely you think Christianity is true, you will always win by being a Christian (or feigning being one). The size of the payoff completely dominates the probabilities.
Your earthly existence, assuming you generally enjoyed life, has a payoff of tb, where t is the number of years you lived. This has to be finite. Nobody is immortal.
So the ratio of payoffs of of your mortal life to heaven is tb/∞, or zero (0). In short, your mortal life is such a tiny fraction of your total existence that all your earthly experiences vanish to nothingness. You may as well shuffle off to the afterlife as fast as you can.
If we change the assumptions to an atheist one, then there is no afterlife. All the afterlife payoffs drop to zero. Which means the ratio of payoffs to a mortal life, to the after life, is tb/0. With denominator being 0, the ratio is ∞. In short, every experience now is of profound value when we recognise its finite. The only way life can have meaning, is if it is finite in nature.
Problem 3: the Omniscience Dilemma
It gets worse if the deity is omniscient (all-knowing) as is attributed to the Abrahamic god Yaweh. Now its not just short, finite life you face that produces meaningless. Because this deity knew before you were born, where you would end up after death. If you're Hell-bound, because say you voted for Hillary Clinton or had some gay friends, Yaweh knows you can't change anything to escape Hell. You'll exist for an insignfiicant fraction of time, before suffering horrible torture. The same argument applies to heaven. Life isn't really a test if your deity already knows you're going to pass and get to Heaven. What possible meaning can life have, if there's not a single thing you can change to avoid your eternal fate?
Summary
The argument atheists can have no meaning to their life is not based on rational deliberation. I suspect rather, it's based on being intimidated by mortality and hoping a pact with an ancient god will allow the theist to escape this. People do derive however, meaning from their lives in varied ways. Living according to the values of some ancient Near Eastern pastoralists doesn't really satisfy the goals of all. Indeed, I'm surprised anyone finds it satisfying.
