If an address is offline for a long time it should be removed from addressbook and name becomes available for new registration. That's the way how inr works now.
But what if owner is not interested to run this resource anymore but want to keep an address for him to avoid scam, etc. We should introduce an annual fee. An address would remain in the books as soon as it's paid. No fee is required anymore if it's back online. In case of stats.i2p, money should go to I2P's budget.
It will not affect people who runs their services. It will let I2P to clean up that huge addressbook from abandoned entries. It will be effective mechanism against squatters. They will have to be online or pay. Even they use some parking page they will need to run an I2P router, that helps the network implicitly.