I always just use "awhile." I think it's an Americanism, like "I could care less."
What I've always been told is that whatever school of grammar you subscribe to, at least be consistent with it. If you've got "awhile" in part, but "a while" in another, and they're both basically being used in the same way... well, people are more likely to notice the mistake.
"Fake it 'til you make it." Should that be just "til?"
