I was going to make a sarcastic comment on that...

But I remembered that a balancer can indeed get off balance: if the outer ring spins. I seem to recall that a particularly cherished or valuable balancer can actually ne rebuilt; with the rubber isolator replaced. However, I have neither seen a defective balancer, nor know anyone whom has had one rebuilt.

Maybe we are all lazy: simply buying new balancers if there is any doubt.