Interesting thread chaps.
Not sure if this is relevant to B744F ops but my previous airline (B763) had some literature which stated that from the moment an in flight cabin fire was declared to be out of control, structural break up could be expected after as little as 12 minutes. Now, if you are at 36,000 feet when the fire starts raging it just about leaves you enough time for a max rate descent and a ditching/crash landing.
Scary!