Thanks for your reply Mutt.
I think that we've got to semantics now. Why on earth would any authority ensure you factor prior to takeoff yet then erase that factor as soon as your wheels are up? That's crazy.
I believe the spirit of the legislation is simple. Before taking off, you have to know you can land factored. I believe that in flight, in normal circumstances, without any emergency, you must still be able to land factored.