A few years ago (almost 2 years ago) it was 2 years. But, it hasn't been that way in quite some time. Please remember that Wiki and other places are not written by Stardock employees (typically), so they are not the de facto answer.
The way our system works is not how Bichur assumes. Basically, when an order is processed, it sets the expiration date in the customer record for whatever term is valid for the sale. If we change the subscription length at a later date for the product, it has no effect on the previous sales.
Please email sales@stardock.com, though and I'm sure they get things worked out for you.