You didn't mentioned Business class or Economy? For business class, to NBO (and other parts of Africa), often you see SA, LH, and LX available but within 2 weeks of departure, so if you are looking for holiday travel there is no guarantee that will happen. ET is good in Business Class, lower end of average in economy. If you're booking business I wouldn't hesitate to book ET now. Definitely advise the same as an above poster, book it as 2 separate one ways unless you're planning on using the Excursionist Perk. That gives you more flexibility if something more desirable opens up at the last minute, though does subject you to double cancellation fees if it comes to that.