I hear what you're saying, but as to half life, I have to chime in that rocks stay around about the same amount of time as someof the materials we put in flies. The question is does the material do any harm to the ecosystem? Lead eyes, certainly. Krytal flash, not so much (but if it's long it might kill a bird that gets entangled in it). Epoxy is non-toxiv once it sets, though I'm not sure what happens to it as it slowly decomposes.
The thing I really get irritated over is the use of stainless steel hooks. I subscribe to the theory that if you're doing it right, i.e. sharpenig your hooks frequently enough, you'll file off the usable portion of a hook long before it corrodes in your fly box. Nickel plating and a freshwater rinse is ample defense against this in the short term and it's only a misguided sense of frugality that leads us to buy anything else. A stainless hook left in the mouth of a schoolie is a death sentence, especially if it still has a barb.
Good topic. Anyone else with a pet peeve or eco-templative axe to grind?