If you have followed the documentation you would have seen that you should incorporate the microflow ASu_CheckMetamodel in your after startup actions. This way with every deployment the model is up to date.
[EDIT] Just checked the documentation but they forgot to copy that part of the documentation over. So just add this microflow to your after startup and you are good to go.
[EDIT] Goto the runtime tab in your app settings to define the microflow:
You can also add the refresh microflow to a Scheduled event and configure the event to run when you need it to. Although the idea of putting it in the after startup flow like Ronald recommended would make more sense as your model wont change unless you do a deployment.