How long can cured LR be out of water B4 die off

[Doo]

No smell at all, I added more LR today and the tank that I got it from is very well established tank with fish in it. She put the LR in a styro box inside a plastic garbage bag and it took me under 10 min from out of their tank and into my tank. I am positive there is very little die off, but I have been always curious as to how long it would take to cause serious damage to the LR...