I am a USA prime account holder with an account that was renewed in January of this year (2014). I was curious why the amazon prime music page indicated I needed to upgrade my account, so, I clicked 'upgrade for 99 dollars'.
It went ahead and renewed my prime account with today's date, and sent me a new welcome email.
It's completely unclear if it has consumed my previous subscription with over half a year left.
My edit expired - Here is the deal. A person can share Amazon Prime with other people - family, friends, etc - but the primary benefits such as this music are available to only the primary email address holder. So when I said 'upgrade account', even though the Verify Prime indicated Active, it was not active for music. The upgrade button instantly charges 99 dollars.
I would ask support about that, Amazon seems to be usually adept at handling such service calls. They handled our complaints in the past that were similar to this quite nicely.
It went ahead and renewed my prime account with today's date, and sent me a new welcome email.
It's completely unclear if it has consumed my previous subscription with over half a year left.
So be cautious... probably I did not read enough!