Here's what I can tell you: the CX500 is actually really easy to work on, but you shouldn't own one if you're not willing to work on it yourself. If you can do that, you can (pretty cheaply!) own one of the most bullet-proof engines Honda ever made. Reports of CX500 (and GL500) engines reaching well over 200K miles are not uncommon with routine maintenance and one or two engine-out repairs along the way.
Basically, there's 2 things that'll make you have to drop the engine: the cam chain and the stator. Sometimes also the mechanical seal behind the water pump impeller if that fails, but there are ways to do that without dropping the engine. They speak of the "Triple Bypass" -- if you have to do one of the first two, might as well do all three.
Usually a bike will make it a good 40K-60K miles before that though.
A good shot of mine: