As a foot note to Lalwende's post, as well as immortality making having children less of a biological imperative, in Morgoth's ring it also points out that the Eldar pass more of their own strength into their children and so they were not able to have unlimited children from that point of you. The extreme example of this is Feanor who took so much strength from Miriel that she chose death - having pointed out to Finwe that the strength enought for many sons had been passed into Feanor ... who himself had more children than any other elf (7). No wonder Nerdanel chose to remain in Valinor
The largest elf families we know of are all in those early generations when the Elves were in the fullness of their strength.
I wonder if part of the reason that Celebrian did not fully recover from her orcish torment is because she had been weakened by having three children at presumably a fairly late age (relatively) - the Laws and Customs of the Eldar state that elves tended to marry soon after reaching maturity (age 50-100) and have their families soon after (in elvish terms.... ).