Btw, the manual does stipulate something:
BHT-412-MM-2 Ch 18 Pg. 33.
Once a main rotor has been product-balanced, it
should not require additional product balancing until a
blade is replaced, or an existing blade is refinished,
repaired, or otherwise altered. Therefore, when
trimming a previously worked main rotor, use pitch link
adjustments and/or hub balance weight adjustments to
correct balance.
I hadn't seen the manual with that update, go figure. The key word here is shouldn't... I do agree that product balance doesn't have to be done everytime the rotor is worked, usually in the intial mode and in forward flight if f/a vibes are higher than desired.
Chuck