Gusto:
However, to keep your FAA 61.75 certificate valid you do need to ensure that:
a) your logbook endorsement from a U.S. qualified examiner needs to be re-validated every 24 months.
Where does it say this----there is no such regulation. You may be referring to the flight review requirement of 14 CFR 61.56 which is conducted by a CFI NOT an examiner.