Every company has issues... just some really stick with the brand. Onkyo / Integra had a disaster that, even though the product has changed since, they still haven't recovered from.
Denon have had some noticaeble sales success in the US of A, I do put quite a bit of it down to the grand standing on the likes of AVS Forum from their dealers like JD Smoothie etc, these sites influence more than many people believe.
For me...
The more channels you jam into a Class A/B receiver, the more issues you'll suffer from. Sure putting a fan inside will keep it cool, but the fans will grow noisy over time and in turn the amps are almost always dust magnets that will then cover the internals and cause more heat / shutdown issues.
But if an amps is failing weeks / months out of the box, yeah, talk to the techs and not the reps - they can't help but be honest.