I think it's safe to assume that the fellow who took the time to make this thread cares. Other wise why would he have asked?
If your SKS still has the original finish, than it is Shellac. Shellac is a great product, however it's not the most durable wood finish. Especially when it's over 50 years old. I don't know of anything that will make the Shellac more durable. I can only recommend to take great care in not banging the rifle off objects.
Buy a can of Shellac for touch ups for when you do smack it off something.