Does human skin change a thousand times?

The entire skin does not “change” as one uniform layer. Its outer layer, the epidermis, is continually renewed as cells mature, move toward the surface, and are shed. Scientific literature gives differing turnover estimates, from about four weeks to 40–56 days. Thus, “a thousand times in a lifetime” is only a rough popular estimate that depends on age, how a cycle is defined, and lifespan—not a universally measured count.