It's possible, but not necessarily certain that those units that just had the new bolt and later failed, had already been slightly damaged or overstressed, and it wasn't obvious. So, depending on the state of the original mount, if it was intact, the stronger bolt may be more than sufficient for the rest of the life of the vehicle. Keep in mind that the original prototypes had accumulated many hundreds of thousand miles and not exhibited any problems with the original design. It may be partly in that the roads in Germany tend to be in better repair than those in some other places, notably, the USA (there's a reason why they have expensive fuel costs...and it's not because the raw fuel costs that much more...it's the taxes they use to keep the infrastructure intact).
Anyway, my very early 2014 US model (made in APril 2014) is still okay, and I hope it stays that way. I understand, no guarantees, but personally, I don't worry about it. If you're really risk averse, consider a later model with the redesigned mount in it. I don't remember exactly when that production change occurred. You might be able to figure it out on www.realoem.com
and look at the diagrams based on build date if someone doesn't remember exactly.