You never want to skip days with Ostarine or any sarm for that matter. They really need dosed every day to keep consistent levels in your bloodstream. The only exception would be with S4 if the vision sides get too bad too quickly, where you could temporarily go to a 5 day on, 2 day off protocol, but even that is not advisable. It's best even with S4 to run a consistent dose every day that is good for you