The United States Nuclear program still uses the floppy disks since 1976. Thats 40 years of usage and while they are are being finally phased out by end of 2017, i would say 40 years is not a bad run.
the article just posted on may 25th 2016 is here :
http://time.com/4348494/pentagon-nuclear-floppy-disks/"If it is not broken, don't fix it?" mindset? But that legacy system that is running for so many years had its ROI many times over.