I'll surely second the comment about that town wearing you down.... I'm usually in Vegas a few times a year (tech stuff, CES, etc.) - by the end of 4-5 days all you can think about is going to sit in that depressing airport to wait for your plane out.
There's something about the Vegas "everywhere you go should feel like a music video" disposition that is nifty for about the first hour.... after that you're totally over it.