Elves- A second puberty?

[MatthewM]

I have always wondered questions like this, in specific beardedness in Middle-earth.

Tolkien gives a mix of ideas, ranging from bearded and beardless Elves to bearded and beardless Numenoreans and those of their blood.

My main question about this has always been, since Tolkien cites that Numenoreans take after the fashion of Elves, if Elves grow a beard in their third cycle of life, do Numenoreans as well? If so, the "third cycle" of a Numenorean's life would be a much younger age than the third cycle of an Elf's life. When would a Numenorean (or one so descended such as Boromir, Denethor, Faramir, Aragorn...) grow a beard? Or did they just shave? Did people even shave in M-e?

The world may never know, but these are my nitpicky questions that I wish Tolkien had answered.