How the sea-shore rotation work in the coast guard?

It depends entirely on force mission requirements, retention levels vs. manning requirements, and available billets, and a sailor's time at sea.

All Navy sailors have established general career paths that include typical sea/shore rotation policies, but they're often negated by fleet needs and mission requirements. Fleet needs come before individual careers, but the average is around 3-4 year at sea and 2-3 at a shore station. Of course any sailor can opt to stay at sea for longer periods, but for a successful career, shore duty is required to gain the necessary experience.

Note that temporary duty ashore doesn't count toward rotation - you must be permanently assigned to a shore station for it to count. For example, though I spent a year going to my second advanced Sonar maintenance school in 1984, it was a temporary assignment from my boat, which was undergoing regular overhaul. When I left, I had 5 consecutive years of sea duty, as seen and recorded by the Navy.