You can also pretty much perennially keep your sub at $1/week w/o talking to a rep just by starting the cancellation flow when the promo rate nears expiration.
For anyone else looking to do this, the trick is to choose "Other" instead of "Too expensive" or "My rate is going up" as the reason for cancelling. The later will just result in them trying to sell other standard subscription offers to you.
Just to be sure I contacted their customer support to see if there was a way to cancel online. They confirmed that there was not, and then had the gall to say that this is because it's better for customers this way.
The content itself is good but I will never ever give money to a company that treats its paying customers this way.
Substack probably has a similar customer base and does things the right way. A paid subscription can be cancelled with an easy to find button. The money I would have spent on The Economist instead goes to several substack authors that I like.