Is Durability Sustainable?

Interestingly, the French word for sustainability is durabilité. And, of course, durability is at the heart of sustainability—isn't it? If a product is durable, it will last for a long time and this means that it won't be discarded quickly, which keeps it out of the land-fill longer. If it doesn't need to be replaced often, the product's total environmental impact is reduced across its lifecycle. On the other hand, if something is designed to last for a long time, does that mean that it won't break down for a long time after it has been discarded—and if so, how can that be viewed as sustainable? Take plastic bags, for example. In the case of a product that is designed to be thrown away after relatively few uses, biodegradability is better than durability. So maybe it all depends on context.