Like, an altcoin? Sure. Go ahead and create a steal-a-coin cryptocurrency where you lose your coins after a while. Let see how many people actually want to use it.
Not an altcoin. Not a steal-a-coin crypto. A can-not-spend-very-old-coin bitcoin for really very old addresses which are not double hash protected. No one is stealing the coins, just marking them as unspendable after they have not been spent 10 years from now (so, some really old coins not moved in 20 years). It was just a suggestion and I have no problem with no one doing anything about them as the coins are unlikely to be spent at all if no one has moved them in the past 10, 11, or 12 years.
This would of course, require consensus and that means everyone agrees to it.
The longest time frame I've seen for fiat banks is 15 years of inactivity, they then mark those as dormant and can "escheat" the money to the state or central bank or whatever. There are procedures for claiming that money. Imagine your great grandfather opened an account in your name when you were a child, put in a few thousand dollars, and you never knew about it until today, some 50 years later.
Why should legacy addresses be treated any differently?
There are some early addresses older than the most recent legacy addresses that were not protected behind a hash of a hash, so those coins can be stolen if enough computing power is put to them. The later legacy addresses are protected by a hash of a hash, so the public keys are unknown until they are spent, for those addresses which are re-used, which is not recommended these days.
I think the earliest addresses have their public keys known? Kindly correct me if I am mistaken. My own first addresses were those hash behind a hash types.
It is good practice for wallets to move coins every year or two but that's besides the point.
Every year or two? Why would that be a good practice? Sounds like a bad idea to me.
Yeah, so you know those coins are still spendable, and maybe to consolidate them as needed. Maybe you don't actually have to spend the coins, but just make sure you can restore from backup any cold storage you have, so you know you can spend them in the future. Of course, this is done either offline or with proper security practices.
I'm of the assumption that these coins are either in cold storage or protected behind a hardware wallet (which is = cold storage too.) If not, and you're still using hot wallets, then it would be wise to move any coins you don't need to spend immediately to cold storage.
Finally, if you suspect that someone may have access to your coins or your wallet could be compromised, you create a new wallet and move your coins there, then you know the new address is secure.
I do have some coins that have not moved in 8 years. They were paper wallets to begin with, I don't think they are moving on their own any time soon.