In Africa there is no hunting at twilight. The PHs pull the plug long before that. My first buffalo was pushing the envelope. We didn't find them until late in the afternoon. The cat and mouse game in thick stuff went on for more than an hour. I began to get a bit concerned. "What if I hit it poorly and we have to run it down in the dark?" I was informed no one goes after buffalo in the dark. "Then it spoils?" Yes. Not much hope of saving a 1700 pound animal even if the temperature did somehow drop to freezing (and in August it sometimes does).
Shortly afterwards it was time to quit, well before sunset. On the way back to the vehicle we happened to catch the herd running across an opening +100 yards away. Glen put up the sticks and they stopped to look at us. "Is it too late?" "Not for you." By then the evening wind was kicking up. "I can't make the shot. I'm moving too much." Glen moved up and braced my right arm. "How about now?" Boom! "You got it! Good shot!" Through the heart and it went less than 20 yards before tipping over. Whew. Later I asked Glen about the range of that shot. "75 meters is normally the max but we knew you could shoot."
The only time I have been in the field in Africa at or after sunset is when an animal has been hit and not recovered. That would be the last animal on my last trip. And I can say unequivocally that if we had not recovered it, that kudu would be my last big game animal. He was hit more than an hour before sunset. A day and a half later my PH got him as I was driving a draw with the trackers. I had hit in the offside front shoulder. Long story. Anyway, every PH I have hunted with hangs it up well before sunset. That is the humane thing to do, especially when dealing with clients of questionable experience. There is SO much game available, it really is pointless to risk having client go home with a bad memory (though admittedly most clients could care less about any unnecessary suffering on the animal's part).