Would it be unusual to see COPD develop in an otherwisr healthy 43 year old male, with a 12-pack-year history of smoking? I have a quit plan in place.

About time. To quit smoking and a great start if you have a quit plan in place. With 12 pack years of smoking you will start having lung damage with certain risk factors. Not on COPD but think of lung cancer and cancer at other sites as well. Quit when you can still undo lot of the damage.