A few suggestions and comments based on your last (great) post, Bhurano. I just want to show that since nobody knows what it's like to be immortal you can pretty much make them the way you want. There is no real logical point behind it.
Psycholgy : So, you're immortal...
a) and jaded about life after the first century and become a thrill seeker
b) and jaded about life after the first century and become a cold rational mind. After all, you saw the big picture
c) and so conservative of your own life that you become paranoid and lock yourself up
d) and turn to mysticism to make sense of such a long life
e) and grow a ponytail while trying to off your own kin in ritual one on one combat
personal favorite : immorality for free makes you consider it meaningless and you're not more concerned about your self-preservation than other species. You would need a very strange psychology to support immortality. Presumably based on active/sleeping cycle. Such long life span would made them more feral than civilized, i think.
The key is to break the logical fallacy that longer life = more civilized and more self-conscious. This apply to humans.
Population : everybody here seems to fear elf overpopulation why really ?
a) elves may not reproduce like us humans. They may be biologically programmed to have a diminishing birth rate based on the population density
b) War, either consciously or unconsciously, can take care of that. Look at W40K orks, they go to war based on the population density, why not apply this to elves ?
c) they are fey and their immortality is based on magic. Why use a rational argument such as food in this case? Maybe they feed on magic ?
d) If everyone fear that elves can SPAM the world with their children, why are they always outnumbered in every fluff i've read for the last decade ?
e) As a last possibility, elves may have to kidnap other species children to fill their ranks for war (taken straight from the Arthur RPG video game) or they could be themselves born in massive waves of elven children based on some cosmic events.
Personal favorite : biology matters more than society in elf reproduction cycle, possibly magic in nature. I'll go with the Bamboo route (http://en.wikipedia.org/wiki/Bamboo) and have them spawn in great numbers at great intervals, thus creating sharp golden age followed by a steady decline until the next wave.
Experience : I'm not sure elves HAVE to be better than anyone else
a) It makes elves prone to have these "i'm so better than any of you" moments
b) Long life is different from rich life, they can live for a thousand years but why should they remember everything ? What if they had a memory span of 1 year ? 10 years ? 40 years ?
c) quality doesn't matter once the other species have access to rifles, at least history teaches us that. Elves can't always be one step ahead. If they are so intelligent, i'm pretty sure they would figure that one out. If they don't have the staying power of other species, they would have to retreat to the fey world and rely on outpost and commando-like troupes for warfare.
Ok, i'll stop there, but boys this topic has me all fired up.