We did end up booking our flight. We chose to go in May 08, SEA-LHR-JNB-WDH rt. I didn't think we could fly all the way to Windhoek using miles, but it worked out.
There was availability for us to go First on every leg, so we went for it and booked. Also, it is great that if something comes up, we can cancel before we go for $50/pp to have our miles redeposited.
I did get one tip that I did not know. You can call 330 days out to book your outgoing flight. Then call back to add on the return flight 330 days out from that time for no charge. Worked great for us.
I hope you can find something to CPT! Good luck