Skip Lot is really Dock-to-Stock. In Dock-to-Stock, sooner or later your system should require a random or structured check.
A typical skip lot would be:
Inspect 3 lots. If OK, Dock-to-Stock for 5 shipments. Check the 6th shipment. If OK, Dock-to-Stock for 5 more shipments.
Continue as long as no nonconformances are identified.
If at any time time a nonconformance is identified, the inspection frequency is tightened - you define what 'tightened' is - such as inspect 3 shipments before returning to skip lot. Some systems are also set up to increase sample size when a nonconformance is identified.