Overclockers Online posted a SilverStone Fan Compendium
SilverStone Fan Compendium
While I can't comment on the 50000 hour lifetime spec, I can say that after running each fan 24/7 I am confident that these fans will perform admirably well into the future. All-in-all I can highly recommend the FM123, the FN83, and the FM83.
SilverStone Fan Compendium
