The system should be easy for the user to learn it so that, when they came back later, they could do their job faster. This means that all the other heiristics points must be taken into consideration and that the system UI must not have any major changes, unless they are extremely necessery.
If changes are needed, they must be done in a way, that should keep the UI as close to the old one, which the users have already learned, as possible.
Techniques for promoting other less used parts of the system, by replacing them with the most used ones should be avoided. An example is Facebook, which recently implemented a new User Interface, which intents to make their users use the chat function more, by taking away some of the most used modules and replacing them with chat options. This is currently causing problems to a lot of Facebook users and most of them are not happy with the change.
In the kiosk prototype, due to the consistent UI design, it is easy to learn and all these layout will be kept in the future of the design.