this thread is a bit interesting and i'd like to chip in on both points.
about 'growing old', first i'd like to alter the parameters a little, if society crashes from PO we'll probably go back to the shorter lifespans of our past, so since we are suspending PO this far anyway, I choose to think of the issue in terms of even larger numbers, assuming (hypothetically) that we continue progressing in areas like genetics and nano-technology, then it's not improbable that lifespans could be increased to 150, 200 years or more.
my take on it, is that continued existence requires mental growth. many people after a few decades of life become like a 'broken record', doing the same thing every day. not taking in any new information or experiences. I see little point in this type of existence other than for comfort and uncertainty about what happens after death.
I'm in my 30's, I have some friends that are significantly older (60's), and they are exactly the type of people I describe, they watch M.A.S.H every day, even though they've seen every episode probably hundreds of times by now, everything is rote and routine.
in such a context, extended (or unlimited) life are worse than pointless, you take up space and resources that could be used by new beings.
for myself, I'm mostly just interested in staying alive for the next 20 years or so to see what happens to the world, people all through history have thought they were living in 'end times', but to be in the generation with scientific reasons to think so is.... interesting.
so, my point above is that a long lived or immortal being, that ceases to 'grow', removes itself from, or at least interferes with evolution (meant in a broad sense of the 'evolution' of the universe, not biological evolution though it applies there as well).
which brings me to my next point, why god can be 'a cruel kid with a magnifying glass'.
first, my general view on relgion and god:
my views are agnostic, I only have ideas about what the nature of god could be, and no beliefs. I see organized religions as plainly ridiculous, obvious control mechanisms, and spiritually unnecessary.
my opinion is that if you believe what anyone else (including me) tells you about a man in the sky or any other such nonsense you deserve the brainwashing you get. my approach is to look at the world around me, and to think about these types of issues as much as possible rather than just absorbing someone elses opinion.
the conclusion that I've reached, is that I don't know squat, and neither does anyone else, so I've decided to do my best, have as little negative impact on the rest of the world as possible, and to just wait and see what happens. I see these as morally and socially sound choices, regardless of whether there is a god or not.
although I think organized religions are generally full of crap, I don't completely rule out the possibility of a supreme being, or that it could be judgemental. although that seems illogical to me.
without going too far off topic, I also think it's possible that if we don't get completely wiped out by PO or global warming or whatever, that we may reach 'omega point' shortly which is the technological side of our exponential growth in every area, we could create a super-ai, which will evolve in a much faster time period than we have. the short of it being that it could functionally be the same as the concept we now hold for 'god', and thus could be a purpose to the universe.
so, the options as I see them
1. there is no god, its all random
2. there is a god, the typical 'man in the sky', one of the religions is right, everyone else is in for it, take your pick and hope your lucky, sorry I mean
righteous.
3. there is a god, the universe is either an experiment, or an 'expression of everything'
4. there is a god, the universe is here to create other super-intelligent beings to keep him company or something.
so, why god could be cruel:
1. well if he isn't there, then yea, that could explain why the world sucks so much, it's an easy logical leap from realizing your religion sucks too.
2. I have no explanation for this one, ask the righteous. it makes no sense to me either.
3. if the universe is 'everything that can be', which quantam mechanics suggests, (at least thats what I've gathered from my laypersons readings), then evil and suffering are necessary consequences of that. likewise if the universe is some type of experiment.
4. this one is the most 'off the wall', but if you read up on the concept of 'omega point' it seems an obvious logical step to me, even if we fail because of our squandering of our resources it doesn't preclude the possibility that another race in the universe might avoid our mistakes.
so, my silly theories aside (which before they get bashed, I will point out are at least as likely as scientology

) , just because religions are obviously false, it does not in my opinion logically follow that there is no god. there may be a god that is *gasp* a bit more complicated than our simplistic notions seems to have room for.
the fact that the universe seems to be a cruel place, is also not a ruling out factor, though I agree it does raise questions, but only for christians and other people with easily assaulted archaic belief systems.
I don't have any definitive knowledge, just guesses and thoughts. a phrase I think appropriate is 'hope for the best, plan for the worst'.
along those lines my thoughts are:
1. if there is no god, then theres nothing to worry about, non-existence is better than hell or purgatory.
2. if there is a god and he's like most religions depict, then I guess I'll spend eternity in hell for not accepting jesus into my heart or eating pork or working on the sabbath or some other nonsense, which will be quite a bummer.
3. if there is a god, and he (it's)
not like religions depict, then possibly something even more interesting will happen next.
I'm hoping for 1 or 3. and my 'plan' for number 2, is to think 'this sucks'.