Vivoactive 3 onhide() not called ?

Writing a watchface and need to save some values.

So, I have

function onHide() {

Application.Storage.setValue("test",mytest);

}

The problem is that onhide() is not called when the user switch to a widget or an application.
Onshow() is called when returning to the watchface.
Is it a bug ?

If not, where do I save my values ?
Is it ok to save them at every onUpdate() call ?

How bad it is to use Application.Storage.setValue for the power consumption ?


Thanks !