Gotcha!
I think the falling out with Bill Bush marked the end. I'm not laying blame entirely on this incident, but using it more as a time reference. Flair had a lot of personal matters to deal with around this time. His WCW contract was only one of them.
Would you consider his '89 program with Steamboat to be the apex of his crescendoing career?
No doubt. Flair talked a lot about that time period in his book. He was mentally shot.
I actually preferred his original fued with Steamboat over the US belt in mid-atlantic as much, much better. They were both young and it was a WAY over angle for a long time. Flair esentially launched Steamboat's career from that point. I watched them wrestle numerous times. The only reason it isn't looked at as a much bigger deal is the lack of a PPV at that point to highlight it. I think it was 77-80 or so. The WCW stuff was very good inring but the backstory and promos weren't nearly as good. Poor Steamer couldn't cut a good promo and Flair was beginning to fizzle by then.
I also really enjoyed his run just prior to and during the Horsemen-era. From a history standpoint the run just prior was probably the apex. He was taking on top contenders in all the NWA territories all over the US and world 350 days plus per year. Just sick by todays lameass standards. His real talent was putting over territory talent to the point of making the locals feel their guy really had a shot to win the "big gold."
The Horsemen era was absolutely electric. ALL promos were a must see....Flair, Arn, JJ and Tully (VERY underrated as a worker and on the mic) could all cut great ones. Not to mention having great competition with Rhodes ( i know you really love him), Road Warriors, Sting, Garvin, Luger (on and off), etc...