pilot and apprentice, all I'll say is- if the shoe fits...then I was probably talking about you. And truly, you sound like one of those paranoid types - as you yourself admit, when you fly high you've always got one eye pinned on what your gearboxes are doing. Why? Don't you trust them?
Oh, and a combining gearbox failure - I'm assuming you're talking about a PT-6 Twinpack here? A "C-box" failure is not the same as a MGB failure. A failure of the combining gearbox would just give you a complete loss of power, right? I mean, it wouldn't affect the ability of the rotor to turn. So in that case it would still be better to be high, to better select a proper forced-landing area.