General,
The degree of risk to blades was associated with the peril to the folks you are picking up and the amount of expected damage. Rarely would an Aircraft Commander risk damage for routine operations, but he might plan to chop 1/2" branches if the folks below were wounded and the enemy was closing. It was common to mow elephant grass in a normal pickup, this would seldom harm a blade, except when a woody bush was hidden in the 6 to 8 foot long grass.
No administrative action was taken if the blade damage lead to some saved souls.
I have seen these decisions made daily back then. Blade damage from branch strikes and bullet holes was prevalent enough that our pathways across the dirt in the troop basecamp area (I was in a Cav unit - hooah!) were paved with Huey rotor blades, and the foot rail in our tiny O Club as an OH-6 blade turned upward.