I have/had an Onkyo 906 that had an hdmi board fail in abt 3 yrs - sitting in 'free air', with a temp controlled set of fans running on it even.
I did read that replacing the caps on it does 'fix it', so, maybe, someday...in the meantime I still use it as a non-hdmi shop amp/radio (it does have HD Radio FM!).
Even with all that and fairly efficient speakers, the thing runs HOT, even at 'idle'.
Still unforgiveable for a >$2k receiver, though, so Onkyo gets no second chance with me (not to mention a nearly inscrutable UI, and weird MP3/lan setup).
Over the years I've just had poor experience with receivers - mostly short life spans, and all seemed to run pretty hot.
It just seems to me that all that is too much 'heat' to put all in one package, only made worse by HDMI/processor boards, so won't ever get another one.
Never had a failure with a preamp or pre/pro yet - I almost got the the Integra/Onkyo pre/pro instead of the 906, and don't think they had anywhere near the failure rate - no amps on board.
Live and learn.