I've done longer safaris (or hunting trips if you prefer), but on a 7 day safari to the Selous, I could have taken every animal on the license in Tanzania. None were (or would have been) "drive by". My trip didn't include the day flying in or out, so it was really 9 days, but I had plenty of time to make 10 or so stalks on buffalo (and took two representative animals). Seven days are not enough, 21 days isn't either....... but if that's what you can do... do it!

BTW, I leave for RSA and Zim in the morning... can't wait!