I would say that the silk fina is the most durable of all the sponges. It is firm with a lovely cleaning surface. It is really difficult to give a life expectancy as each sponge is so different and it depends on the frequncy of use, the manner or use, what sort of products are used with it and the dry conditions. I am sure there are more variables too. As they are unbleached, they are expected to have longer lives than the bleached ones and we do only ever try to send out good speciments.