How Long Do Ford Trucks Run???

Im writing on behalf of my boyfriend wish i think is amazing story. A ford truck 1999 diesel dual wheel. With amazing mileage on this truck 320, thousands miles. Which he uses almost everyday between holding horses or for work he makes a living racing horses. He has been transporting horses from Pompano to Pennsylvania making several trips back and forth. The truck only needs minor things done and still keeps running to get him here and other places he travels. He does alot of driving and this truck still gets him to where he needs to reach. Way too go for Ford trucks.