Actually, they can do a 100% purge of voting registration after each and every election, requiring people to sign up again each and every time. It is well within the state's authority to do so.
I thought that a registration should only last for a specified time (say 10-years, expiring in odd numbered years to prevent any election year issues with voters not registering in a timely manner) to defacto purge the rolls automatically.
I hate the logic of "there's no proof, so why should we do anything", when its relatively simple to ensure one aspect of the voting process at least has a mechanism to ensure only eligible people vote. And we're not just focusing on dead people, but also those who have moved. What exactly is the mechanism for the state to validate these people, unless the person notifies the state? I work with someone who was active duty and was a legal resident of Florida. He recently retired and started working for us and was no longer a legal resident of Florida, but now was a legal resident of Maryland. He registered to vote in Maryland, and tried to cancel his registration in Florida, but they made that process so encumbered that no one would go through that just to remove themselves.