There are two different windows within which it gets deleted. You can redownload it if you couldn't watch something within the time allotted.
Here are the details (OntapTV works similarly, if memory serves):
http://mybroadband.co.za/news/broad...now-offers-downloads-for-offline-viewing.html
Up to 25 TV shows and movies can be stored at any one point using the app on Android. Storage is also limited by the capacity of the device.
The content will be viewable for 30 days, and once you start watching an episode or movie it will be available for the next 48 hours for you to finish. The same content can be downloaded again if needed.
*EDIT: For people without home Internet, I think it can be pretty great feature. I wonder how many folks without home Internet have access to decent broadband at work or elsewhere, and can justify the R89 or R99 to subscribe to OntapTV or ShowMax, though?