I know that some seats are blocked for status holders, but would they keep the block even when no other seats are available for selection by Silvers or below? The only time I've ever been upgraded is on the return leg of holiday travel in March this year, from KEF to LHR. Not a very status-heavy route I guess, lots of tourists like myself on the flight, a bunch of us were upgraded from a similar area on the plane to make space for a decent sized group of Chinese folk who were all travelling (and sitting) together. Everyone that I could see getting upgraded was also of status. Sadly I have never had the chance to experience business class long haul.