I've never heard of Warhammer elves not needing sleep. Are you sure you're not getting them mixed up with DnD elves?
A) I never said they didn't need sleep...
a self-induced coma-like state
were regularly beyond them
Never did I claim they didn't actually sleep, only that they're entire existence is so quick and yet so slow at the same time - Elven minds, for example, working faster than any Man could hope to manage - that proper sleep is not something they do regularly...in this case as often as other races.
B) He's a Shadow Warrior, part of a perpetually vigilant group of nomadic Elves that wander around the Shadowlands keeping a look-out for their hedonistic cousins. It was an assumption on my part that they likely didn't get much sleep.
And C) I'm getting them mixed up with nothing, good sir, in fact I pretty much made up the entire thing based on what I considered to be plausible; the thing about all WHF Elves is that things such as their need for sleep, their sexuality, their metabolism and so forth are generally unknown/unanswered by GW. We even know more about the Dwarfs, including more of their language, with Elves being very much like Tolkien's own in that not much is known about them, their society, or anything else.
Novels such as The Sundering series of books and Gilead's Blood go some way to addressing such things, but generally only the most learned of Human scholars have even scratched the surface of such things.
Hope that answers the question. :)
EDIT:
Most people look at WHF Elves like Humans with shiny armour and pointy ears, as if they're relatable to us in any way expect their bodily form and basic functions, when they are more like aliens from another planet to anyone except an Elf-friend or another Elf. Much like the 'Eldar' in 40k - mysterious, arrogant to a fault, near immortal, and with a capacity to do things that just makes them seem all the more alien/magical.
It's why I found it odd that your character knows so many Elves - even as a Marienburger - and that pretty much all save one of the group were just like "eh, it's just some Elf who suddenly turned up, it's a regular occurrence."
I'm not saying everyone's characters should immediately flip-out or anything, but I know how I'd react if I was in close proximity to a more-or-less immortal being with entirely black eyes, soundless grace, and abilities that seemed to me superhuman almost. Not quietly, and not without questions.
Still, plenty of time for those!