My primary Overlander is my '11 Silverado 2500. I forget the exact mileage, and I'm in the Bay Area for work and the truck is home in Vegas so I can't pull the exact mileage, but IIRC it's just under 140k miles. Some might think that's high for something you're trusting for your life-support "off-grid" but I've had enough new vehicles to know that anything can let you down and you need to be prepared for a vehicle breakdown even if you just drove your rig off the dealership lot. To me being prepared for a breakdown means Sat Comms (like an inReach), enough food/water to last the longest you could reasonably expect a rescue crew to make it to your most remoted location planned on a trip, the right clothes/gear to survive for that same time in the most extreme weather you could possibly face in areas your going, etc. Also, I'm over-the-top with maintenance. My truck got switched to all Amsoil synthetics a few thousand miles into its life (after a reasonable break in). I'm talking engine, trans, t-case, both axles, power steering, coolant, etc. I change the oil ahead of schedule, even though the Amsoil should allow longer intervals. I change the trans fluid every 2nd oil change which is WAY ahead of schedule and every trans fluid change I do the spin-on filter, ever second trans fluid change I also do the in-pan filter. The axles I've changed every 20-30k which is way ahead of schedule, but with the SAS the front is obviously now non-stock and the rear got fully rebuilt so I now plan to change them annually (which will prob only be ~10k miles). I'll prob just do PS annually from now on with the big tires to turn. Fuel filters I do way more often, but more on that...
I also pay attention to known potential issues on my specific vehicle. In the case of the '11+ LML Duramax that is the CP4.2 high-pressure fuel pump. It's semi-common for them to go out sometime after 100k miles. Generally it happens to poorly maintained trucks, especially ones that pushed fuel filter changes until the dash warning comes on. On the D'max trucks there isn't a factory lift pump, so the high-pressure pump has to pull the fuel all the way up to the engine from the tank which they are not particularly good at. As soon as it's fighting a clogged up filter it becomes really hard on the CP4.2. On my truck I added a lift pump with additional filtration and did a CAT fuel filter adapter on the factory filter location so I have 3 total fuel filters (one of which is a water separator) and I change them often. Anyway, when my truck hit 100k miles I had the CP4.2 changed out (for another new OEM unit, yes you can buy modded ones but I've had poor luck with non-stock parts too many times). While the front of the engine bay was ripped apart I had the water pump, every rubber hose/line/belt, every clamp, every pulley or idler/tensioner, etc. etc. etc. changed. None of them were "bad" or showed signs of failing soon but it was just "worth it." IIRC the whole job was somewhere $2-3k, if I have to do that every ~10 years or ~100k miles I'm a-okay with that vs. having the CP4.2 fail and take out my whole fuel system (a $4-5k DIY job, $10k dealership job).
My other two Overlanders are 100k+ too, my Xterra has ~145k and my WJ has ~110k (but is getting a new motor, rebuilt/upgraded trans, just got new axles, the t-case was just rebuilt, etc. etc. etc.).
-TJ
