Think of how much people throw away each week. A phone is only a couple hundred grams and takes up a small amount of space. Think of how many phones could fit in a single garbage bag. The number will be way more than the number of phones they will go through in their entire life. So in your entire life you are saving a fraction of a garbage bag's worth of garbage.

Right, but it's not the weight that matters, it's the environmental impact. And there I'm convinced that e-waste is not negligible.