The Federal Reserve shreds 7,000 tons of worn out currency each year. As you
probably guessed, the note most frequently replaced is the $1 bill. There are currently four billion $1 bills in circulation, and the life expectancy of each is approximately 18 months. Bills of larger denominations stick around longer since they are handled less than the $1 bill. The Life Expectancy for the $5 bill is 2 years, for $10 it is 3 years, for $20 it is 4, for the $50 and $100 bills it rises to 9
years.