Well, I live on gravel roads. And I frequently travel to off-road parks to ride ATVs where there is sand, dust, and grit in the air all weekend. And I have aftermarket wheels that stick out 3/4" farther than stock with mud tires. I have zero issues with the paint. Very first thing I did was install the OE style fender flares to protect the lips of the wheel wells, and rubber mud flaps to protect the rocker panels and area near the rear bumper. I don't have any issues.
Last month I did a concrete job and in a STUPID move I mixed the concrete at the rear of the truck so that I could just roll the bags of cement mix off the tailgate into the mixer. Ended up with splatter of concrete mix all over my tailgate and rear bumper that dried hard and solid and wasn't noticed until a few days later due to all the dust and dirt on the truck. I scraped it, no luck. Washed it with a sponge, no luck. Used chemicals, no luck. Finally tried vinegar and a brush and was able to get all the concrete splatter off the paint. Looking at the truck now, you can't even tell it ever happened.
In my opinion the paint is great on these trucks and the clearcoat is thick. I'm happy with it.