XGDS 20 or 30 for most stuff, 70 is .. exceptional
by Stu Friedberg
The bulk of SI material is exempt from the general declassification schedule, with typically 20 or 30 year hold times. Of course, that doesn't mean it's declassified after 2 or 3 decades. It just means that the classifying authority doesn't even have to reconsider the classification until that time.
It was my impression, as an Air Force guy working in a combined services location, and sharing a barracks with NavSecGruDet Augsburg, that the Navy plays a lot of stuff closer to the chest than the AF or Army.