Fact is, vehicles only have so long a service life. You can keep pumping money into them like a money pit, rebuilding every item thats failing, but in the end you still end up with a worn out old truck. At sometime you have to know when to hold them, and when to fold them. As far as an arbitrary mile goal.....imo, it makes no sense just to wear out a vehicle with no reason, except to aimlessly to wander around the countryside without a goal to be there. I did enough driving in my younger days racing bikes, but at least I had a goal when it came to the end of the day.....a wall full in my den room.