For your QuickBooks Online subscription to stay active until January, I suggest paying the monthly plan on time. To make sure your funds are fine and you're not too close to the due date, you can set a monthly reminder on your phone a week before the due date.
In case you want to know the date when your subscription ends, you can check it in the Billing and Subscription page in the QB Settings. I've added a screenshot for your additional reference:
I've added these articles to help you manage your subscription in QuickBooks Online: