So I woke up this morning in one of those strange brain moods pondering random things. Finally my semi-conscious thoughts settled on Tolkien. The numbers are pretty hard to make work
There were 144 Initial elves sometime in the middle of the first age. Then after a bit of time they were called to Valinor. Many others died in the Journey or ended up going to Valinor. Then some came back, and other stuff happened blah blah.
But their birth rate is absolutely paltry. They live for thousands of years, but seem to generally have 1-3 kids in their lives, with dudes like Feanor an exception with 7(but he was an exception in all things really). And It’s not like they all turn 16 and pop out their spawn, They have them after living a lot of years.
So either those first Elves were humping like bunnies/had much higher Fertility, or the First age must have been half a million years or so to account for the Numbers of Elves we seem to see.