One other thing you can do for resilience, is periodically (say every 6 months or so) take out a full page ad in The NY Times with the hashes. These newspapers

One other thing you can do for resilience, is periodically (say every 6 months or so) take out a full page ad in The NY Times with the hashes. These newspapers tend to be archived all over the world by multiple people, and are another way to provide proof that something was published by a certain date.