In an average lifetime human skin completely replaces itself 900 times.
According to a 2011 study published in the journal Environmental Science & Technology, we shed between 0.03 and 0.09g of skin every hour. That sounds like almost nothing, but over the course of a lifetime it adds up to about 35kg, or roughly half your bodyweight. Most of this is in the form of tiny flakes, which make up a major constituent of house dust.