I've only sent an all time favorite once, and probably never will anymore even though it got 9.5/10 on the one occasion I sent it. I don't know, I just don't like the risk of an absolute favorite song of mine getting bashed even though it's with completely fair points.
And that all time favorite was apparently being used to death in roulettes by others so that was kind of a turn off aswell (Alter Bridge - Blackbird by the way)
EDIT: Also, those all-time favorites are mostly songs I tend to be overly confident in just because I like them so much for reasons no one will have after just 3-5 listens.