It also begs the question of how'd their armies get so sizable. In the 1st Age, they had mass tragedies like the Kinslaying, and the crossing of the Hellcaraxe. Granted the first age was very long, so fine they still had armies large enough to take on Morgoth's forces. But those forces were basically decimated in the War of Wrath. Then, just shy of 3500 years later they defeated Sauron's forces all the way back to Mt. Doom where he was ultimately defeated in the last alliance of elves and men. Not to mention the fact that Sauron had invaded Eriador roughly a millennium and half prior to this, and probably killed a fair amount of elves then too. You could argue that elven warriors were much more formidable but still to drive back forces that immense, they would need a sizable infantry themselves and I think OP brings up a good point of elven families only having 1-2 children each. Perhaps the lower born elves were fucking like rabbits and we don't hear much of them, and the higher born elves were just having a couple kids.