mini USB: octobrer 2000 to january 2007 (6 years, 3 months)
micro USB: january 2007 to august 2014 (7 years, 7 months)
USB-C: august 2014 - ? (5+ years)
I hope we keep increasing the lifespan of the "suggested" mobile-device USB form factor, to increase convenience and (slightly) reduce environmental impact.