I wonder if they changed that, I thought I had to renew it a few years ago.
Ah, according to the wayback machine, it used to be 5 year:
http://web.archive.org/web/201108131...-eng#rn_link05
Then it went to 6 years, then 7, finally March 2 2015 it went to permanent. Yay for archives! Proving me not crazy once again!