SAA's web site says that the required check-in time for all international flights (except to the US) is 2-1/2 hours before flight time. Are they serious, or is this just the typical airline blather of "hurry up so that we can make you wait"?

I'm taking SA's NBO-JNB flight in a few months, and it's now scheduled to leave Nairobi at 0730. Very difficult for me to believe that I either have to -- or even can -- check in at 0500, but then again I'd feel very stupid to show up at 6:15 and find that the flight is closed. Unfortunately, I'm traveling on a UA-issued RTW ticket, so I very much doubt that I can use telephone or online check-in.