Thanks, Smithy.
Lack of mil-spec components means more incoming inspection, including thermal cycling, required to achieve a mil-spec equivalent.
The small amount of heat generated by the electronics in a really cold Wx radar antenna isn't going to raise temperatures very much.
By definition, an airplane is a group of compromises flying in close formation, and the Wx radar antenna is, too. You have to balance the increase in failure rate of the electrical components from power cycles, vs the additional wear of the mechanical components if operated continuously. If the antenna is the older design with no electronics, then mechanical wear is the only factor.
As I alluded earlier, the Wx radar system is reliable enough that operational considerations take precedence over reliability. Probably most US airlines never turn on the radar except at night or when convective activity is visible. If it were required all the time, there would be no on/off switch on the fright deck. Fully half the Wx radar removals in the US occur in TS season, mostly in August.
Back to the 767: the Wx radar is powered only when a pilot has pushed the WX button on his EFIS control panel for display on his EHSI.
GB