I think if you have a read through some old threads you will be able to answer your own questions.
Visa application times vary depending on many factors. My guess is Kenyan application would take minimum 12 - 14 months since it is a high risk country. But again you should check your allocated embassy website for more accurate wait time.
Some people try to time it (medicals and police check) so that it is completed a few months before their visa is granted. e.g. after 6 months they get their checks done. Others wait to be asked. Generally it is recommended to wait a little if the published processing time is 12 months or more as these checks are only valid for 12 months. Also i read something about if/when you get your visa granted, it expires the same time as your health/medical checks so best to have a bit of extra time for yourself to get your things in order.
Note: I am not a migration agent or expert so please do your own research/seek advice.