Having now covered 63,000 miles in my 4/4 with no sign of a fastening becoming loose I see no reason to tighten them. Dry fusion or light corrosion is likely to keep things together for longer. Overtightening could lead to stretched bolts or stripped threads or deforming what is held. Fastenings that have been disturbed during the servicing process have a dab of white paint across their mating surface and as yet show no sign of loosening once left alone.
