I think the list of spares has to be personalized. What might work for a full timer might not work for someone who is out to a rally and then back.
There are obvious things everyone should carry such as belts, lights or bulbs, fuses and CBs, relays and miscellaneous common hardware items. I carry a tire plug kit, extra Schrader tire valves, and stuff that is always handy like velcro, double sided foam tape, RTV silicone adhesive, duct tape, nylon wire ties, extra hose clamps, and spare cabinet latches.
I used to carry a spare tire, spare brake chambers, and fuel filters. I don't any more.
But more because the bus is a convenient place to keep things together I have a Webasto control unit, the boards and a fan for an inverter, a spare blower motor for the Webasto heat exchanger, a fuel pump for the generator, and some wire and a collection of electrical terminals.
As important as the "stuff" I carry however are my tools. In addition to the various hand tools, probably the most used thing I carry is my multi-tester.
We all will tend to gather our own collection of stuff based on what we are capable of repairing while on the road, and what we have had fail in the past.
