I just got done cleaning the underside of my RV hood. It was dirty and I didnt like the way it looked so I washed it and waxed it... Cleaned everything else under there too..
I'm one of those "nuts" too. Have always washed my engine compartment several times a year, but, got into the habit young with hotrod vehicles and my later years with Dodge Viper, Saleen Extreme and supercharged Jeep. Just like seeing any potential leaks/issues early and yes, does help upon resale. Careful around the fuse boxes but otherwise a good spraying does wonders.