To be fair, I don't think he said he was finished with his search for knowledge. He seems genuinely interested in the way the world works, and for his own sake (not anyone else's) it seems he would continue that interest.
He has said that he's come to some conclusions about how the world works, for instance that we all die, or that the universe will come to an end. These seem to me quite safe conclusions.
Can we be absolutely certain about them? No. But that doesn't mean that we should not base any actions upon them. They are pretty solid conclusions, and unlikely to be overturned.
Now, if his philosophy naturally follows from those conclusions, then I'd say it makes sense to follow his philosophy. As an individual, because that's all we're talking about right now. Why? Well, we have a cost-benefit analysis to do. There is the possible reward for altruism (as a catch all term for all selfless acts that he is preaching against), if everything turned out ot have a point. We can view that "reward" as anything we like, it doesn't matter.
On the other hand, if you follow his advice (live for yourself, today - and honestly, that could entail keeping up social graces, paying taxes, etc. as an entirely pragmatic consideration - if it helps make your life happier), then you live the happiest life you could.
So you are left with two possible lives, one in which you are as happy as possible, one in which you are much less happy.
You are also left with two possible outcomes - one in which nothing matters, and one in which everything you did, or did not do, matters. I mean matters on some cosmic, rather than individual scale, as that's what we're talking about when refering to whether or not the universe will "end".
I would argue that based on what we know, the second outcome is so unlikely, that even though the reward might be great from a life based on the assumption that it could be true, such an investment is unwarranted. For much the same reason that I don't play the lottery. The investment might be small relative to the possible return, but the chances of getting that return are tiny.
Basically, your argument seems to follow similar lines to pascal's wager. "We may not be able to show that god exists, but we should worship him just in case." seems quite similar to, "We may not know if the universe has a point, but we should assume it does just in case." Both to me seem so unlikely that it isn't worth making that wager.
Just as a quick follow up on what I just said, I don't think his point is that science can't ever change it's opinion, of course it could. But to think that is as likely as that it will expand it's knowledge but keep the general story basically the same seems to me to ignore everything we know. Yes, it could turn out that the universe will in fact not end. But it very probably will.
Here's an analogy. Imagine I'm watching a baseball game (please note I know very little about baseball). It's the bottom of the 9th inning, and the team I am supporting (call it Team A) has is up to bat with 2 outs. The score is B: 12, A: 0.
A friend I'm watching with casually says, "I'd bet you $50 that team B will win."
What do I do? Do I take him up on his offer, because, after all, anything could happen? Or do I base my decision on what I know about the game so far - that team B is a stronger team, that A is in serious trouble?
Of course Team A could win. It's not that unlikely. But it's not worth making the bet - my expected payoff is less than my investment.
The evidence that the universe will come to an end is much stronger than the evidence that team B will win the game.
Of course none of this suggests that I agree with his conclusions. As I've argued above (in other posts), I don't see how the "purpose" of the universe (or lack thereof) in any way affects me or my life.
Ah, hell, we're all hypocrites sometimes.
Well, according to his philosophy, on an individual level (for him) it does, because of the opportunity cost. He would say, "I could have been much happier, which is what I want out of life, if I'd acted as though the universe would end." He just feels that this opportunity cost outweighs the possible benefits of betting that there might be some hidden purpose after all.
the story is still pretty awesome.
