JL2:
I'm not sure of the answer. I think the 30 day window only applies to European/Hawaii flights. When I bought my ticket EWR-BKK on CO to NRT and NW beyond about 3 months before departure, I was also upgraded at the time of purchase since there were seats available. In neither instance was there ever any discussion of the 30 day window. The key issue appeared to be the availability of "Z" seats with CO.