"Crysis Warhead - the nail in DirectX 10's coffin"
Gameplayer's PC guru has put both versions of the CryEngine 2 (one in Crysis, and the second in its recently released expansion Crysis: Warhead) and documented his findings in this article.
"Warhead suffers from the same 'gradual slowdown' as Crysis. It's worth saving, then quitting out of the game once an hour or so to clear it out. Presumably some sort of memory leak, it hits worst in the ice levels."