Some subscribe to preventative maintenance, others say let it break and then fix. IMHO my shop is the place to do maintenance and that is enjoyable to know when I leave it is ready for the road.
I learned that when I had a JOB and that required I got back home to be back to the JOB on time. Even today with no JOB I still do not enjoy sitting along the highway or in campground waiting until part arrives. Working on coach along a highway with the drivers of today is no treat. If it is gonna fail it will be in some remote place on usually Sunday afternoon with no potential for quick economical fix.
If it is suspect part, install new one and keep used part as spare. Doesnt cost any less but somehow your mind doesnt look at it as if you spent money foolishly. What you never will know is if it prevented a break down - but that aint all bad.
If you travel the highways which we just did from southwest Arizona thru New mexico, Texas, Louisiana and Mississippi to Alabama, then on into Florida, even a new rig gets stressed heavily so preventative maintenance is a must to keep you rolling. I have no idea where the southern states are spending their federal dollars on the Interstate highways as they all are in very poor shape.