Aside from using it too long, is there anything that can cause WEP to become un-available?
Was flying a P-51D earlier and couldn't use WEP. I had not used it at all that flight, all I had been doing is climbing at 200 MPH, pressed "P" and......nothing. Tried to extend away to figure out problem but couldn't shake off Zygote, got shot down and re-upped for a test, it worked fine (of course it'll work when I don't need it).
And broke my keyboard from pounding on "P". Fortunately I got it working again although it sounds funny.
I think this is all part of the global conspiracy against me.
J_A_B