Four hours is all they usually allow - in case your samples are of an explosive nature, and you don't return. Dumb or not, that's the rules as I know of them.

Added:

That being said, just walk up and check in - after all, you could be going to the lounge to sleep until the flight, and don't want to go back through security.

[This message has been edited by msn (edited 06-05-2002).]