It seems this question is easier to lay out as a 'word problem' so here goes:

The Smiths have been happily married 30 yrs and are in their 50s

In 2016, Mrs. Smith inherited a home in Georgia, and moved there from TN, taking up residence and changing her car tags, license, and voter registration.

Mr. Smith continues to live and work in TN. His employer pays the expenses for his domicile in TN (rent, utilities, cable) as an incentive for Mr Smith to stay. He has a TN license and is registered to vote in TN.

Mr. Smith visits his wife's home in GA about a week out of each month, sometimes "working from home". The Smiths have always filed a joint tax return.

Mrs. Smith no longer works outside of the home, but makes a very meager living selling things online, for which she pays Schedule C taxes. (She has yet to make enough to be required to file under GA law).

For 2016, the Smiths filed as residents of TN, where there is no state tax.
They want to make sure they file properly re state taxes, and not get 'dinged' later.
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Question:
Should the Smiths for tax year 2017 file as full-time residents of GA?
or
Should they file with their residency situation separate, with Mrs Smith being full time and Mr. Smith part time based on the time he works in GA?

Thanks.