Some questions about Elves, the Halls of Mandos, and Valinor

[Galin]

Originally Posted by narsil

1) When Elves die, their spirits are transported to the Halls of Mandos.

The spirits can refuse Mandos incidentally (just to note it).

How long do they have to wait there until they are provided new bodies? And barring Glorfindel, has any Elf returned from Valinor to Middle Earth after receiving a new body?

Inziladun already noted it...

'It was therefore the duty of the Valar, by command of the One, to restore them to incarnate life, if they desired it. But this restoration could be delayed* by Manwe, if the fea while alive had done evil deeds and refused to repent of them, or still harboured any malice against any other person among the living.' JRRT, Last Writings, Glorfindel II

*Or in the gravest cases (such as that of Feanor) witheld and referred to the One.' Author's footnote

3) Why is Valinor forbidden to mortals? Tolkien made it clear that it wasn't the land that provided immortality, it was the races inhabiting it. So why should it be forbidden to Men, Hobbits, and Dwarves?

I believe the description from Akallabeth might be a bit misleading (moths and flames and so on): Tolkien goes into this statement deeper in a text in Morgoth's Ring, explaining that a Man -- though he might live out his whole life in Aman (the same amount of time as his whole life in Middle-earth), he would feel himself to be a fleeting thing by comparison to the world around him.

For example: if a 20 year old Man planted a sapling, he would be dead before it grew as it might in only one year upon Middle-earth (in mortal lands). Time was not different in Aman, that is, one 'year' in Aman was really 144 Sun Years long, but as Legolas noted in connection to Lorien: growth and change are not the same in all places.

Aman better accorded with the Elvish speed of growth, but Men will be as short-lived moths, 'withering' soon to our perception.