Killing Maia

[Knight of Gondor]

Well, how long did it take Gandalf?

I think there is at least one aspect for which we can find some kind of vague reference.

Gandalf, as I understand it, "reported back" to the Valar, as in "I was sent back". They were the ones who sent him back. Sauron and the Witchking did not "report" to the Valar. And I believe it only took a symbolic three days (try reading the New Testament if you don't know what it's symbolic of, ) for Gandalf to return in physical form, albeit clothesless. He just had to be hefted to Lorien where he could get him some clothes. (You stop imagining Gandalf in Lorien without clothes! That's an order!)