My limited experience with amidol is with the M&P formula. Michael, your formula was written on my darkroom wall until recently, and I painted over it as we were selling the house and I am sure the buyers would not understand.
Yes, an M&P solution of amidol developer lasts a long time. Over night in the tray, no problem.
It is no magic potion. But it certainly is different. Blacker.
The stuff I have was culled from a darkroom garage sale, way pre-chinese, and it does stain fingers and toes and anything else it touches.
As stated above, the chloro-bromo papers stand up best in amidol. Ektalure is very nice in amidol.
In any event, about the benzotriazole. It's good to have on hand. As a restrainer, it remains constant in solution, whereas bromide levels build. It is most helpful in lith printing.