You discovered one of the amazing aspects of Kodachrome. I've seen 50 year old slides shot on Kodachrome that still looked like brand new. It's primarily due to the design of the film and the way the colour is created on the film's surface. Ektrachrome is a "subtractive" process where all the colours needed are built into the film. During processing, the "unneeded" colours are removed by the developer and the bleaches. Kodachrome is a "dye additive" process so that whatever colours you photographed in your subject matter are applied during processing. The film basically "grabs" the colours it needs during processing. The dyes are very stable and (as you noticed) don't fade with time. For example, look at 50 year old Technicolor movie prints...basically the same "dye-additive" process.
The slides can still be degraded by fungus if they are stored incorrectly, but they last FAR longer than any E6 process film (Fujichrome, Ektachrome, etc.) out there. As you also discovered, Kodachrome is damn sharp. A few of the current E6 films have equalled it but it took them a LONG time to get there. Unfortunately, Kodak has all but abandoned Kodachrome as it is a horribly polluting film process and Kodak is the only company who can develop it (there might still be a couple exceptions to this, but precious few). I had a chance to shoot a few rolls of medium format (2-1/4 inch) Kodachrome back in the mid-80's but the format didn't last long due to such a limited user base. I've even heard about large format (4x5 inch) sheet film Kodachromes but I've never seen one. That would be jaw-dropping imaging.
The Technicolor Company could process pretty much anything, but the "Technicolor Process" is a different animal altogether. In fact, somewhere after "The Godfather" was printed and released in Technicolor, the company kind of went away. The last I heard, they had sold all the equipment needed to make Technic' prints to China. Somebody correct me please, but that was the last rumour I heard. The materials used to make Release Prints today are very, very good and it sorta made Technicolor a costly line item. Actually, I've read interviews with film restorationists (that's ONE reason I love what Steve does!!) talk about the quality of film stock they have to work with today. They are now able to pull out more detail both at the highlight and shadow ends of the scale than they could 40 years ago thereby negating the need for the Technicolor process. These guys fight the same battles that Steve does with regard to deteriorating original elements; however I've never heard Steve talk about a reel of tape going up in flames the way the old nitrate film stock can do.
As to Grey Market film, you probably can buy it without TOO much worry given the global nature of commerce these days. There was a time when I wouldn't go near it since you never knew how long it had been in transit, how long it had been sitting on a container ship (maybe on the top of the stack), etc. etc. If I was going on a "once in a lifetime" vacation, I think you'd be crazy to risk it to save a few bucks. At my paper (when we still shot film), we wouldn't go near it despite the enormous savings we'd realize. It just wasn't worth the risks plus we felt that we should be buying our supplies through "legitimate" channels. Also, we were buying "Pro" film stocks (shipped at maturity, not "green" like amateur film) that are refrigerated from the moment they leave the factory (supposedly) because the emulsion is ready to be shot NOW and not left on the shelf. If you're doing something that isn't colour-critical, I'd say goes for it. Or, if you can get a few rolls of each, I'd shoot some tightly controlled comparison tests and see which one you like best.