See The time, on average, between the first issuance of a banknote and its withdrawal from circulation by the issuing central bank. High-value denominations usually have a longer average life than low-value ones which, due to their more frequent usage, deteriorate faster. More, Ratio between the number of banknotes per denomination that return to a central bank, during a certain period, and the average number of banknotes in circulation during the same period. It is one of the indicators used in the management and analysis of cash in circulation. More.