I took The Mule in for some post-tour TLC. In the process I learned a few things about the bike’s components.
Rear hub: The rear hub is badly worn. (The wheel wobbles a tad from side to side.) I had new wheels built for this tour but for some reason didn’t replace the rear hub. Since the worn part is no longer made, I have to replace the hub and have the wheel re-built. The shop that did the original build is giving me a generous discount on the labor.
Rear derailleur: The rear derailleur is starting to show signs of age. It has a bit of lateral play independent of the shifting mechanism. I can probably get some more miles out of it but I am putting it on the winter to-do list.
Front derailleur: For some time now I have had problems shifting into my small chainring. I had at least five mechanics look at the derailleur but none of them could solve the problem. Just before the tour I took the bike to my local bike shop where a mechanic finally fixed the problem. I have no idea how long this fix will work but everybody I have talked to who knows about these things says the problem is likely a worn spring in the mechanism. Add a front derailleur to my winter to-do list.
Rear brake: My rear brake has been giving me fits. It’s hard to work on and never seems to work properly. The head mechanic at my local bike store told me why. Bike brake mechanisms are actuated by levers. The Mule has short pull levers. The front brake is compatible with its lever. The rear brake, which is made by a different manufacturer, requires a long pull lever. The result is a mushy feel to the rear brake lever and very little room between the brake pad and the rim.
The distance between the rim and the pad is set using a tiny screw that pushes against the end of a tiny spring. If these get misaligned, adjustments to the brake pads is extremely difficult. I am definitely replacing the rear brake this winter. I may pay big bucks for a Paul brake that, in addition to being compatible with my short pull levers, uses a wrench instead of a tiny screw to adjust the pad/rim gap.
A Few Spokes Shy of a Wheel 
The question begs to be asked: If you are going to do all this work and put a lot of money into it, why not just get a new bike and donate the Mule to the Smithsonian?
Maybe because it is still a solid frame worthy of new parts?
I keep expecting a mechanic to find a crack in the frame. The Mule is still one tough bike
I’ve actually looked. Touring bikes are hard to come by. Good ones can cost well above $3k
Wow. It’s never ending. But this bike has been through so much with you, it’s like a friend at this point.
It’s 32 years old and has over 72,000 miles on it. It’s insane!
I won’t tell you what I think, because you already know. Lol.
But I totally get it. It works for you.
Mark,
The more I think about this the more I’m leaning toward a “it it ain’t broke” mentality. The shifting works fine so I’ll leave the derailleur replacements until it degrades. The wheel is obviously broke so I’ll just ride it until I take it in for rebuild. Might as well.
My only concern about the Paul brake is fit. It’s going to be tight, based on the measurements on the Paul website, I need 81 mm of vertical clearance for the cable. Oddly, the video on the website seems to show that my exact set up should work. I’ll probably have this done at my local bike shop this winter or when the rear brake breaks my sanity.