I left my norinco SKS for about a week once after shooting a couple hundred rounds of the Czech stuff.
There was signifigant rust in the bore, on the gas system (especially the gas piston), the bolt and bolt carrier, and even in the magazine!
I'm figuring my SKS will last about 1 more crate (3 crates total) before it seizes up. My bolt is rusted "bubbly".
Pretty much, as soon as you get home from the range, rip it to pieces, and scrub it to hell. The bluing/treatment on Norinco SKSs does not at all prevent rust.