They just keep them around for a few years. Recently, they just had a big sale of material going back quite a few years. The Mint has a long history of this. Personally, I think they should take orders for a limited time, and then strike coins to demand. A second, although less desirable, alternative would be to mint the coins and sell them for a predetermined amount of time, and then melt what's left over. But, no. Instead they Mint way too many coins and keep them around forever. Witness the Pittman disaster from the late 1800s - 1904. Then, sixty or seventy years later they get around to releasing bags of mint state Morgan dollars. Don't get me wrong...I'm glad the coins were preserved, but the collectors who had mint state examples had to be ticked, as their value was destroyed overnight.
