You can get a 1, 3 or 5 year subscription for $20/year:
As an existing user, that specific promotion wasn't available for me. Also, my yearly bill is $29.99 instead of $39.99 - probably a grandfathered price?
Anyway, when I went into my account settings (My Account > Account Summary) and clicked on Extend Premium Now. I was offered the same rate as the new user rate from the above promotion for a 5 year extension - $99.99 for 5 years. It just displayed it to me as a 33% savings, but still came out to $20/year.