Here in Georgia if one hasn't voted in any one election in last six years, federal, state, local, school board, splosh, primary, general, runoff, probably more I forgot. At least 25-30 different elections take place here in a six year period, then if they haven't voted in any one of them, they're taken off the registration roster.
In other words, if one hasn't voted in six years, they're not going to vote, period. All it takes to stay registered is to vote just once every six years. Once will do nicely.
Georgia's problem is that the county voting registers aren't notified of anyone deaths or if they move to a new address, location or out of state. I personally think that law is a good one. Without it, it would be just a matter of time before the registration roster of a county would have more people registered to vote than live in the county.
This never remove anyone off the registration roster is a bunch of bunk. I think giving a person six years to vote before removal is valid and makes common sense. Vote just once in six years, you're still registered.