Bwana: Two hours is fine. Google along the lines of "power outage fridge temperature 2 4" for some really good links.
When the 4 hour outages were posted, and a thread started on this, I mentioned the 4 hours were pushing the safety issues. Also - and this is a bigger issue - "open" fridges etc in food stores cool faster - and not all shopkeepers are that, uhm, concerned as to the quality of their merchandise. While I am aware that the health practices of a shop keeper are not the responsibility of Eskom et al, it is concerning.