Didn't read the whole thread but here are some things to consider:
- Carefully set current limiter to ~5-10% more than the minimum you think you need power-wise. Will keep motor temp down and help run-time
- Pack all bearings with a waterproof grease, something a little heavier than what normally comes with them. Same w/Diff outdrives.
- If one of the cars has the option to run the rear shocks forward on the rear arms, use that. In 10hrs you could get packed and have a shock unecessarily damaged
- Take advantage of the conservative motor/esc settings and use a body with fewer vents to keep stuff out of the car
- Shock boots if you don't already run them
- Put more padding under your RX.
- Set your servo saver a little softer.