The average life span in months for a $1 bill.
The U.S. Mint, as directed by the Presidential $1 Coin Act of
2005, is promoting the use of dollar coins as a green alternative to
the greenback. The mint says dollar coins last decades and that their
use could save the government billions of dollars over many years. The
Mint has minted more than 1 billion of the new presidential dollar
coins since January 2007. Four designs are minted each year, honoring
the presidents in the order in which they served.