Not unless you want to! If you're already a subscriber just include a little note to us reminding us of that and we'll tack on your new year's worth (or single issue) to your current pre-paid issue count. Currently paid up through Fall 2012? Now it's Fall 2013 with the $85 level, or Winter 2012 with the $22.
Don't see the answer to your question? Ask the project creator directly.