KRS 286.3-180(6) (http://www.lrc.ky.gov/statutes/statute.aspx?id=14547) discusses giving 90 days notice, to the Commissioner of FI, if any operation of the branch is discontinued. I did not see a definition for operation and I’m not sure how this is interpreted or enforced by the KDFI. You could take the safe approach and provide the 90 days notice or contact them to find out what is required.
You would also want to consider how it could affect CRA and document the Change/reduction in hours/services in your public file.
228.43(a)
(5) A list of services (including hours of operation, available loan and deposit products, and transaction fees) generally offered at the bank’s branches and descriptions of material differences in the availability or cost of services at particular branches, if any. At its option, a bank may include information regarding the availability of alternative systems for delivering retail banking services (e.g., ATMs, ATMs not owned or operated by or exclusively for the bank, banking by telephone or computer, loan production offices, and bank-at-work or bank-by-mail programs);