From my experience, there is no everlasting digital system, no matter how many fallbacks you add. So I wonder, how can you ensure, this still works after e. g. 1 year?

The system checks with contacts after one year to reconfirm. If I don't receive my weekly check-in email I check the server. This is a best effort attempt to ensure business continuity for me if I'm dead. It's better than not having a plan for me. There's a health address you can point to that checks the system is working from an outside monitor. :)