When is the best time to use emergency build?

[CW]

I don't get it, EB can be sustained for 1 year, how come it went into slow build after only 3 or so turns? Did you accidentally deactivated it?

I think there is a case here for a UI improvement: Currently when you click on the EB button to deactivate it it will go into slow build immediately, bad luck if you clicked on it accidentally. I think that nothing should take effect until the "close" button is pressed, so that you can undo the deactivation if you really pressed on the button by accident (it happened to me quite a few times before too, but I saved so often that I didn't lose any work.)