Re torqueing head studs/bolts

Every time that you tighten a nut/bolt, it makes the bolt/stud stretch a little. Some of the stretch is permanent.

If you loosen the bolt/nut then retorque, then you now restretch the bolt again.

If you just torque it to the torque again and not loosen it, you don't introduce another clamp cycle of stretch into it...

After 5 clamp cycles, the bolts should be replaces as they may now be more prone to break...