As long as either of your other balancers have never loosened up they should be as good as new. No sense buying another if you have two spare ones.

Until they spin in relationship to the crankshaft they remain exactly as they were made. I have not had a balancer loosen up myself on a mercedes but have observed the issue by many others.

I am going to think about this all too often reocurring issue on site a little over time. I doubt there is a way around it but there may be. The issue is the method would have to be usable by the majority.

I have a suspicion that the manufacturing tolerance in production of the two tapers might have been too great. A really good taper lock fit is very difficult to separate. The impulse loads from the engine are large in my opinion as well though.

I almost discount the accessory loading in comparison. In otherwords even without the accesories the balancer could eventually loosen up if the taper is out of tollerance..

Also a friend of mine keeps raving about a certain type of glue he uses at work. He has told me it is unbelievable in strength and was designed to bond clean metals. I will get and try a sample of this out on something.

That also reminds me that the balancer and crank snout taper should be cleaned well with laquer thinners before fitting. The effort may or may not be worth anything but it cannot hurt in my opinion. It might even promote a little oxidation in there. That increases grab I suspect.