Publishers determine Wii U demo play limits

As is the case with the 3DS, Wii U demos from the eShop come with play limits. You can only boot up a demo a certain amount of times before it becomes inoperable.

According to a Nintendo representative, publishers determine how long demos remain on the eShop and how many times they can be played.

“Each publisher has the opportunity to decide how long demos will stay on the eShop, and how many times consumers can play them before they expire.”

When content expires, you’ll receive the following message when trying to start the demo:

“This demo can no longer be used. View information about the full version in the Nintendo eShop?”

If you select yes, you’ll be taken to the game’s eShop page.

Source