The FAA private pilot certificate (PPL) does not expire, however to continue acting as pilot in command (PIC), you must meet specific currency requirements which are described in the FAR.
You must satisfactorily complete a FLIGHT REVIEW BFR every 24 calendar months to act as a pilot in command.
The flight review, which can be administered by a CFI consits of at least one hour ground instruction and one hour of flight instruction.
After you have passed the fligth review satisfactorily, the cfi will endorse your logbook.
Do you need a CFI for flight review? contact me at andreas.rosquist@faaflighttraining.com