Recently, I read that one should never leave a kiln unattended.

We recommend that you monitor the kiln during operation. This does not mean giving it your constant attention. Just check on it occasionally, especially toward the end of the firing. This advice applies even to digital kilns that shut off automatically. It is a good idea to check on glass before the kiln shuts off. This is to make sure it has fused to the exact degree that you had envisioned when you designed the pieces.