Neupielot: In my experience of the A320 series, if you watch the leading edge after having selected the wing antice on, you can see the ice being shed from the leading edge. Once the flaps are selected to F1 an air gap opens up therefore the wing antice hot air is lost and the system is not effective and may therefore be switched off.
Incidently, the A330 & A340 seem to be much less prone to the build up of ice on the leading edge.
(return to bunker ready to accept incoming ............... )