How to save sushi for later?

Could you please elaborate on the best methods for preserving sushi for future consumption, ensuring it remains fresh and delicious? Are there any specific ingredients or techniques that should be avoided or prioritized to maintain its quality? Additionally, how long can sushi typically be safely stored, and are there any signs of spoilage to look out for? Understanding these details would greatly assist in enjoying sushi at our own convenience, rather than just immediately after preparation.