I had gotten in my head that you were booking now for travel after 1 March. Does a B-UP "stick", or do the CO systems require that you be elite at the time that the flight takes place?

Certain other airlines (e.g., UA) periodically do sweeps to make sure that people seated in E+, for example, should be seated there. I have read anecdotal reports on the UA board that people who book E+ in January but lose status in February are reseated once their status expires.