Having skimmed this thread I can't be sure if the following has been raised?
Assuming a Platinum Suite, the Discovery Miles benefit for credit card transactions will pay you back a MAXIMUM of R100 for a R15,000 spend (assuming you are on diamond vitality money). After that its a much lower return of 1 rand per R1000 spend.
For those of us on bronze (as I currently am), the R15,000 spend translates to a miles benefit of R30.
While I understand that there are other benefits at play, where is the incentive to 'spend' to get Miles?