Carnival stock has nearly doubled over the past year. The party might not be over.The tailwinds have been strong for Carnival (CCL -0.83%) (CUK -1.21%) and its fellow cruise line stocks. All three of the country's largest operators rose at least 7% on Wednesday, and Carnival shares have nearly doubled over the past year.There's a lot to like about a giant in an industry with bullish momentum, but has Carnival been coasting too far for too long? Is it still a buy, or is it time for investors to disembark fro ...