Anything that you can catch only once will respawn after defeating the Elite 4 if you run from battle or knock it out.
Ah cool cool thanks munch. Now to fight them and catch me a Thundurus finally after years and years.
....years and years? It's been nearly 2 years/a little over 2. That's not "years and years". --- I'm told I look a lot like Rory Macdonald - http://i46.tinypic.com/2eyf5sy.jpg Set to WARNED status for being a Republican on 11/08/2012