I've started naming my App Engine apps bemmu1, bemmu2... so that if I decide to discontinue an app later, I can just reuse one without having an old name still attached to it. It doesn't really matter as the name would not usually be visible to a user.
I am more concerned about the 13(?)-app limit.
10, but we can increase it if you ask.
Who would we contact about an increase?
You can always just empty your app.yaml or edit your code to return an empty page...