funny options, true dat! In my case it usually loops, like dream in a dream (inception, lol). But still it's mostly uncontrollable, you may think you are in charge while you're actually not.
The directed dream usually ends when you come close to your desired destination because you become too excited and too conscious about it and it doesn't flow naturally as an uncontrolled dream would (though too much excitement almost always awakes you in any case)