Use the modern buses like the Modern Oxygen and you will be fine. In 2018, I left Kenya in the evening arrived in Kampala in the morning and left Kampala for Nairobi in the evening of the same day. I wouldn't recommend that though. But I was fine. If you ain't returning in a period of less than 48 hrs then you are good.
You are truly the village champion u even dont like AC hihiiii enjoy ur stay in kenya let them give u real nyama choma with that ugali and kachumbari u will lick ur fingers huuuuu