Well, my promotions were pretty automatic. In the Canadian Forces back in my day, you got your first chevron (private [trained]/able seaman) after 30-36 months service and the second chevron (corporal/leading seaman) came after 48 months service. After that, it depended on your performance. As I stated before, I was just too bored, so I doubted I would have been appointed to master corporal (two chevrons & maple leaf) after 2 years as a corporal.
Canadian lighthouse to U.S. Warship approaching it: "This is a lighthouse. Your call!"