At what point would one consider leather seats beyond the ability to be restored? When it feels a certain amount of stiffness, or when it starts to crack up?

I ask this because I have come across two Brooks saddles, one is on a friends bike and i think it might be able to be revived, the other is on a bike the has been sitting on campus for most of the semester, which appears to have been abandoned (I'll ok it with campus security first, but it is a schwinn super sport with broken cables and it looks like someone already made off with the rear wheel.) It looks like it might be cracked and I was just curious at what point the line would be crossed for end of the road.