if i buy a BitBill (or some similar "offline-bitcoins") today, you want them to become worthless in 20/100/1000 years and i can't think of any reason to do that.
you want me to send my coins from address A to address B every 20something years and again i dont get it, what difference does it make? none
My original proposal was to allow recovery of coins from a lost coin pool if you did indeed retain the key, which would protect things like BitBills.
The only problem this might run into is if the lost pool doesn't contain enough coins to cover your recovery claim, in which case you'd have to wait for more coins to enter the lost pool. But they would eventually be made whole.