OK. It took some doing, but I think I got it figured out so you can buy several months at a time instead of going monthly. First, you'll have to upgrade to a monthly plan and checkout like normal. So this will purchase the first month. The upgrade might even be free because many times there is a credit to your account when you switch to a monthly plan.
Here's how to upgrade to a different plan:
To upgrade to a different plan, go to your Manage Purchases. Find your active supporter badge and click the Manage button. Right below the product information is the Upgrade/Downgrade link. That will allow you to upgrade/downgrade your plan to another one.
Here's how to buy several months at a time:
After you upgraded and you want to buy several months in advanced, go to your Manage Purchases. and click the Renew Now button. From here, you can choose how many months you'd like to renew for. (You can also do this same thing for a yearly membership too)
It's also worth noting that these new memberships will auto-renew. If at any time you want to cancel the auto-renew, you can go to your Manage Purchases. Click the Manage button. Then below picture, there is a Cancel Renewals button. Click that to cancel your auto-renewals.
Don't worry, I'm going to put this tutorial in the Articles section. If at any time you want to manage your SSV Patron account, click the Support SSV tab on the top navigation bar and choose Manage Patron Account, then choose Manage Purchases.