I don't think anybody knows for sure. I recently used some 11 year old Quaker State 10w30 semi-synthetic in my wife's '97 Expedition 4.6L.
I didn't notice any ill effects from using this oil.
I'd say in a dry, room temperature environment, 10-15 years would be a good "estimated" shelf life for any modern engine oil.
I have often used 10 to 12 year old oil with no ill effects. Since finding BITOG I no longer stockpile oil since I've learned that oils have improved so much in recent years.(this may not be true with the recent SM change). GC may be different because I'm not sure of the life expectancy of an elf.