I have not ever used wing anti-ice in almost 4 years flying the 747-400.
It is listed in the FHB as "ineffective" with the flaps down, so it is useless for takeoff and landing. Further, we can't legally take off with any ice or snow on the wings anyhow.
In the times the ice detectors have alerted us, I have not seen sufficient ice on the wing LE to bother turning it on.
OTOH, we use nacelle (engine) anti-ice quite often...