Hmm that's true; I also know I never find all the typos until I narrate my book, and I'm always reposting titles with corrections and back matter updates, so that would be problematic too, having multiple versions forever out there. I'm still learning about smart contracts, which you could use to automate sales and delivery, and you could set to terminate every 90 days, replacing it with a link to a new contract or none / no link if you go into KU again. The book is still out there but termination of the smart contact leaves it on the chain but inaccessible... This is all theory of course. Thanks for making that point!