I don't register every bill... I sometimes go months between getting the urge to put some bills in the system. But it's sometimes fun to see what turns up.
I thought belatedly of entering the bills in my pockets during my travels last weekend. I should have paid for my coffee in the Philadelphia airport with a registered bill, and then watched where it went. I did add a few later in the day, and spent some registered bills in Atlanta that weekend and then back at PHL on Sunday night. None has turned up yet, but I bet bills spent in airports get lots of mileage!