New 72 hour exempt rule

Hi,

I am an American Citizen, holding an E2 visa in South Korea. I would like to travel to Beijing and Hong Kong at some point. I currently have 7 months left on my E2. But for those two destinations, does it matter if I could be exempt with the 72 hour exempt rule that was implemented for 2013...or do you still have to have time remaining on your E2 if you plan on coming back to S. Korea.

Thanks!