I had to get an international ticket reissued today due to a schedule change. Got transferred to a great agent from the Global Support desk. We made small talk and I asked him about some of the questions about extension. He pulled up their internal documentation and also confirmed that CB will be offered just for extended status level.
The thing he added that I have not seen here (unless I missed it) was that the status extension offer can only be rolled over for a MAX of 5 years (at a cost of 500k MQM).