You're right, they really do!
I didn't notice until today. When you start your wallet up and the blockchain starts catching up, your wallet balance starts trickling down.
I assume that given enough time, every Freicoin in existence will eventually disappear into nothingness. How strange!
They don't disappear, what is get from demurrage is sent to the blocks.
You lose around 4.9% of the original value every year, so your coins to totally fade away you would wait almost the aeon.
This is correct. It will take ~15 years for half of the coins you have to recycle to the miners.
nethead is incorrect in saying these coins go to the foundation. The foundation only gets a percentage of the initially mined coins. The miners get the demurrage fee (technically -- its not the same coins, but the exact same number of coins).