I don't recommend this, as the longer you keep the raw fish, you risk bacteria growth and illness. If I find that we're getting full and we still have ingredients left, we'll usually just enjoy the rest of the fish, thinly sliced sashimi-style, because that's the most valuable part, and let the rest of the ingredients go. Also, refrigerated rice gets hard and dry, and doesn't reheat well, so this is something that should be eaten freshly made.