The minimum maintenance expiry date for 4.5.43 is July 1, 2020, the same as 4.5.38.
In general, if the Software Updates window notifies you of a version that's outside your maintenance, it shows a message that says "Your maintenance has expired", and in recent versions it replaces the "Download..." button with a "View Details..." button. If it doesn't say your maintenance has expired then you can click the download button and install that version.