Dox,
it all depends where the blind is set up - at a waterhole or close to a trail
Waterhole -
it depends what animals you are after as not all antelope have the same drinking habbits. I am sure the farm-owner or guide will be more than helpfull with the best time for what-ever antelope you are after.
Trail -
again - it depends what you are after on the day. I have hunted (rifle) many times in the Kalahari and i can assure you the people there know their farms and animals intemately. From my experience - they will have the most accurate suggestions for you to be where at what time for what animal.
Good Luck!