the main benefit your friend will have is the tank won't develop rust spots inside since it has been kept full.
If the gas sat for greater than 6 months to a year, then I would recommend siphoning out as much of the old gas as possible or draining the tank if that is easier, draining the carb, and refilling with fresh gas before trying to start up the bike.
He can put the old gas in his wife's car for disposal.....
