Thanks for the input. As to whether it's necessary: I do hit the occasional rock when mowing, and when my blades get out of balance, I can feel more vibration coming through the mower deck. I'm assuming that it could lead to earlier spindle bearing failure, but not sure.
I sharpen with a flap wheel on an angle grinder, and it's a simple matter to make a few extra passes on the heavy side of the blade to balance it out.
But I hadn't thought about the difference between static and dynamic balancing, and can see how that might make a difference. I'm hoping that by removing material from the full length of the cutting edge, rather that just from the tip, I'm still getting consistently improved results.
Even if the only benefit is a slightly smoother ride, there's no reason not to do it, imo, given that it typically adds just a few minutes to the sharpening routine.
My previous mowers' blades all fit fine on the cone balancers, and I was happy enough with the accuracy. I've tried the nail on the wall, but I got much less repeatable results with that method.
The quality balancers from Oregon and others go for $80 - $90, and I'm not willing to spend that much. So I'm now thinking about a bearing with the right o.d. to fit my blades, and that I can mount somewhere on a vertical surface in my garage. Cheap enough to give it a shot.