I heard somewhere it was common practice to reuse tablets. It was easier to scrape the surface clean than to make a new tablet.
You'd save any tablets you have, and might wait until you need it to scrape it clean.
In Mesopotamia there was a period where it was fashionable to use a more rare softer red clay on top of the white clay. Your stylus would cut through the top layer leaving nice white letters on a red background. It made it easier to scrape clean and reuse, but much less durable over time.
