The tablet should have been allowed to be destroyed
Throughout the movie, Ack and his parents are the only real people among all the "animated" humans, i.e. Lancelot, Owen Wilson and the Romans, Teddy Roosevelt, the native american woman, etc.
They lived real lives, they died, and here they are, continuing to live. It's creepy. Ack even jokes with Teddy Roosevelt about Lancelot not knowing he is real, while the truth is that apart from Larry, Ack was the only real person in the gang. Honestly, I think the tablet should have been destroyed. Imagine if someone with evil intent got their hands on this tablet that allow them to never die at night. They could use it to be basically invincible.
In this movie, even paintings come alive, so imagine the actual extent of that power and how it could be used.
I wonder if the tablet could make the Statue of Liberty come alive, or any other giant statue. We could have Godzilla vs Lady Liberty fighting in Manhattan in some sort of Night at the Museum/Godzilla spin-off.