[Fred K-OR]

I would think what you carry as spares depends on where you drive your rig. If you only drive down to the local coffee shop (like I do a lot) that is different than if you drive across the country. The coffee shop run I take my cell phone so I can call my wife if I need help. If I would go across country, then I would think about a number of spare parts that could need replacement on the trip. The reason for the spares is that you don't find a Model A repair shop or a willing Model Aer to help in every town you go by. Model A being a different breed of rig than your modern.

So it would seem like where you drive would determine what you take with you.