If you have any background at all in the Geological Sciences then you should already understand the effect that scale has on the oft-repeated hysteria that to dump a liter of used fixer into a septic tank once every two or three months is tantamount to creating a new Superfund site. A geologist understands scale. Both in regard to volume, and especially in regard to time. Applying arguments of scale to such claims goes with the territory. Or should.
If your point is rather to assert an economic argument that wasting money is bad after the initial outlay to concentrate the resource, we all know that. But that's not a resource argument. It's an economic one. And a very, very good economic one. Everyone should be using John's silver magnets. But not to save the earth from silver down the drain. Do it to save yourself the money down the drain.
As far as the silver itself goes, you can recover silver from your fixer until the cows come home, but at some point the cycle will terminate. One of your as yet unborn great-great-grandchildren will be cleaning out their attic, look at your old silver photo, not remember anything about it or you, and toss it. Where it will then be picked up by the disposal company, put on a truck or train, transported to an approved landfill, and... be returned to the earth from whence it came.
And there is nothing you can do about that. You're going to live 50-100 years. The earth has been around for 4,540,000,000 years. Google-up The Pale Blue Dot. We are for all practical purposes a closed system, whether you want to acknowledge that or not.
Given all of this, here's a question for you...
What exactly, at the most fundamental level, is the crime against Nature in removing silver from one hole in your backyard (a mine), then depositing it into another hole in your backyard (a septic tank)?