We will keep track of how many months you've already paid for.

When you're ready to upgrade to a lifetime subscription, the months you've already purchased will be counted as a credit on your account.

For example, eg.) if you've bought 4 months subscription time, you can pay off the difference. That counts as $399.99 towards the purchase of a lifetime subscription!
(Orders placed through upgrading can only be fulfilled if your customer file has the prerequisites, so please double check!)