The U.S. Treasury estimates that the average life of a one-dollar bill in circulation is 5.9 years. Roughly six years ago, I was obliged to spend a one-dollar bill (series 1993, serial number L 67301723 C) in a vending machine outside Ashland, Maine. It was brand new when it was given to me, and, accounting for the presumably low vending machine traffic (or indeed any other kind of traffic) in and around Ashland, Maine, I suspect it's reaching its shelf life right about now.
So, here's the deal: anyone with the time and inclination for scavenger hunting who wants to track me down said one-dollar bill, I will give you a less beat-up one-dollar bill and have your name retroactively added as a co-inventor to U.S. Patent No. 5,614,39X.
Happy hunting.