Letters Home WWII (2)

Some of Dad's letters to his parents are dated.  This one was written on 31st Dec 1943 and it was postmarked in San Francisco Jan 6 1944.  It seems almost incredulous that it only took 6 days to get to the US and during war time.  Dare I say that the postal service was more efficient then than now.  Not only did it arrive in the US in 6 days but each and every letter had to be opened and examined by the army examiner before being mailed to families.  Not sure if that took place here in Australia or in the US. 
At the end of the letter Grandma has written a comment before the letters were sent on to other family members.