The performance does tend to fall off as they age. How much is still a variable, based on lots of factors but 50% in 10 years may not be totally out of the question. It is hard to find hard data on this.
As for getting rid of bad ones, it all depends on your local land fill rules. It is not any worse than an old TV or PC board. I assume once these become prevalent, there will be a program for safe disposal but that is part of the long term cost.
