I believe you have to re-purchase a subscription for every "section". A section consists of:
- Season
- Playoffs
You can either purchase a subscription for the Season Only, the Playoffs Only or a combination package that includes both the Season and the Playoffs.
Since it works that way, it's based on a season, and you pay monthly. You're probably allowed to pay in one go as well, but I believe that's how it works.
This would mean your payments should've stopped at the end of the season, and won't "roll over", since you only purchased a season or a season + playoffs.
Hope that helps.