I'm afraid I've been away so long that the boards are overwhelming... my work schedule prevented live participation in this entire season, and the podcasts have been all I've been able to manage. By the time I listen to one there are 10 more pages of comments piled up
But I've heard something mentioned several times that seems partly related to this thread - the idea of the maturation of the Eldar, and the dearth of information on the subject. There is actually a very tantalizing bit in Morgoth's Ring, "Of the Laws and Customs Among the Eldar..." It's obviously too long to type here, but some major points of JRR's own thinking:
1. The Eldar "grew in bodily form slower than men, but in mind more swiftly."
2. "There was less difference between the two Kindreds...in early youth; and a man who watched elf-children at play might well have believed that they were the children of Men."
3. "This same watcher might indeed have wondered at the small limbs and stature of these children, judging their age by their skill"
Long story short - the Eldar could already walk, dance, and speak by the age of 1. But by the age of 3 men were growing faster physically. A roughly 18-20-year-old elf has a body like a mortal 7-year-old, but reasons like a mortal young adult. Elves took about 50 years to reach the 'suspended early adulthood' phase, and 100 years to become 'full-grown.' (These ages are drawn from the text, not imagined by me)
Herein lies the connection to this thread. The Eldar would 'normally' marry at around 50 (being quite intellectually mature, though physically behind men). Children would be born within a short space (in Eldar terms, not mortal ones - we would find it long) after marriage. As for the number and timing of their children, it was not limitless:
1. The Eldar cannot bear children at any random age - they do in fact have a limit (the timespan of Arda) and do reach an age where it is impractical, because:
2. The Eldar spend more of their spirit on childbearing than mortals, which limits their ability to conceive - Feanor's 7 sons is a rare exception. Seldom more than 4 in early generations, and even fewer in later ones.
3. The Eldar never actually lost the
ability to conceive. However, after spending much energy 'begetting and bearing' a few children, their
interest naturally turned to other things. (Tolkien's words: With regard to generation the power and the will are not among the Eldar distinguishable. Doubtless they would retain for many ages the power of generation, if the will and desire were not satisfied; but with the exercise of the power the desire soon ceases, and the mind turns to other things.)
This is admittedly an obscure text, and Christopher Tolkien has a hard time dating it. It could also present some jarring points to viewers who expect Elves and Mortal Men to age similarly. But, it's there to work with, if we want to. I know there's a desire not to portray the Elves as simply "men who don't die," but to reflect the fundamental difference of their relationship with time. So, it could be helpful.