Hi
Obviously the channels/feeds we are talking about are currently on a relatively insecure encryption and keys do become available.
As said previously, the provider ticks the box and does the necessary to stop the majority viewing the content. That said I'm sure that the provider is well aware that their content can be viewed by the few with the correct equipment and information.
I have no idea of what contracts there are in place between the supplier and the encryption provider but that contract will or should have an end date. At the end of this contract then yes the broadcaster may choose to use a more secure method of encryption, cease broadcasting or may continue on as before.
As said certain channels using this encryption have been available for years and at some point (probably end of their current contract) upgraded making them unavailable without the correct subscription.
So who knows how long these channels/feeds are contracted for and when that end date might be. As far as changing codes every few weeks or days then surely this would be in the contract and may not be able to be changed without negotiation and or additional cost.
As seen recently the BBC have tentatively made the decision to cease BBC3, but if this goes ahead then this would not be until Autumn 2015 (18 months away). This is probably as they have contracts with content suppliers, broadcasters etc and cannot stop broadcasting the channel until then.
So I can't see these channels/feeds being majorly affected until outstanding contracts come to an end or are renegotiated.
But be aware, these contracts could end or be renegotiated tomorrow, next week, next month or even in five years time. Without that knowledge who knows how long it will last.
If your going to spend your money trying to receive these channels/feeds then be aware they might not last that long!!!
Hope this helps