Love it. This is spot on, as are all your observations.
Run collecting isn't done, and it never will be for me, and I'd wager many others. I still get a thrill of filing away something like a 10 or 12c Tomahawk which fills in a run of eight to ten unbroken issues, or maybe even thirty issues. Then it's on to that missing issue of Strange Adventures, or as you saw, Mystery In Space - or a Superboy, Blackhawk, Jimmy Olsen, or perhaps a missing Adventure featuring the Legion...
The non-key covers present a similarly pleasurable assault on your visual cortex every time you pull one out of the box, especially a dinosaur or gorilla cover. Or maybe even a Gold Key painted cover. Comics are perfect little time capsules which fuel memory bubbles.