It also depends on the usage rate. JR Central tends to rotate the shinkansens after 13 years or so, but JR west has been known to get more years out of their rolling stock. The 700 rail stars are 24 years old, 500 series 27 years, and the 8 car N700 8000/7000 are 13 years old and there is no replacement ordered as of yet. E3 and E2 still running north of Tokyo, some are over 20 years old. Its not impossible to get 20 yesrs out of a single frame depending on usage rate.