I do the IAD - NBO flight about six times a year on KLM

ticket prices are so high intra-africa that there really aren't to be many good options for MRs. Plus, as noted, until KQ joins skyteam (which they have been on the verge of doing for 2 years now) you're not going to earn EQMs

when they do join, you could take DL to Johannesburg and then up to NBO on KQ. That would be about 21k miles, and fits the MR acid test of being pointlessly convoluted