Yes out of date gravy can be eaten as long as it smells good and has no bad taste to it.
If the canned gravy is bad it will smell bad or have mold in it but as long as the canned gravy has never been opened it should not have any mold or bad smell to it.
Canned gravy can last for a long time past it's expiration date.
The expiration date means that the gravy is not as fresh but the gravy remains safe to eat past the expiration date as long as it's remained sealed.
Canned gravy does eventually go bad but it takes around 5 years or longer for the canned gravy to actually go bad enough to where it's no longer safe to eat.
The gravy being sealed in a can makes it last longer than it would when out of the can.
I've heard that canned gravy is no longer good 2 years after the expiration date on the can but I've actually had some canned gravy that was in a house I bought and the canned gravy was 10 years old.
I thought it was gonna be bad and was gonna open it up and see and the canned gravy was still good and safe to eat.
So you can keep canned gravy for a long time before it goes bad.
After 10 years it may not be any good but I've never kept any canned gravy or any canned foods that long.
Canned gravy is good well past the expiration date so there's no need to throw the canned gravy out or any other canned foods past the expiration date.