I didn't really find out anything accurate. The Australian Embassy Nairobi website did say 12 months, but people were saying that's not accurate, so who knows. I also read that the Nairobi embassy can be ridiculously slow, for no reason other than it's Kenya! TIA!
We haven't done the application yet, as we've had some other delays, but with the potential that it could take 12 months or more, and the medical and police clearance only being valid for 12 months we were going to wait until they are requested. We live at the coast so don't want to waste a trip to Nairobi if we have to repeat it.