Sausage Gravy will last from 3 to 4 days when kept refrigerated once you open it.
If the sausage gravy is canned gravy and it never has been opened then the sausage gravy when in a sealed can will last 5 to 8 years before it gets to the point of going bad.
Homemade sausage gravy will last 4 to 5 days in the refrigerator but when you freeze the sausage gravy it should last 6 months to a year.
If you open a can of sausage gravy you should eat it soon after or refrigerate it if not gonna eat the leftovers before 2 hours.
When the sausage gravy sits out longer than 2 hours it begins to grow bacteria which is bad and can make you sick.
So refrigerate or freeze any leftover sausage gravy or any other gravy to prevent it from going bad.