How often should I replace my Insoles/Arch Supports?

Under normal use, a pair of high quality Insoles/Arch Supports should last the user a six months to a  year. However, a firm answer cannot be given because many factors are involved. Such as the brand, the style, how often they are worn, the type of shoes they are used with, the activity the user does when wearing the Insoles/Arch Supports and several other factors.