In the past this was a rare occurrence but SA has been making a bit of a habit of Journeyblitz lately. Now to coincide with Black Friday etc. they are offering it this weekend again.
There also seems to be more availability; I have found (and booked) seats on a date that wasn't previously available. Could just be coincidence of course...
So if are trying to clear your account or you have miles expiring in March, tuck in.