Snail mail from Raro?

Dear Editor, I was very surprised, while staying with an old friend in Auckland, to find letters I wrote and posted separately to him on January 10, 14, 16 and 21, all postmarked February 13 and arriving together on February 20! Does this mean Post Office waits until it has enough mail to warrant a shipment? Nothing will spoil my memories of a wonderful (fourth) trip to Raro, but next time I will not try so hard to write a postcard every day to my children in the US and UK.

Dear Editor, I was very surprised, while staying with an old friend in Auckland, to find letters I wrote and posted separately to him on January 10, 14, 16 and 21, all postmarked February 13 and arriving together on February 20! Does this mean Post Office waits until it has enough mail to warrant a shipment? Nothing will spoil my memories of a wonderful (fourth) trip to Raro, but next time I will not try so hard to write a postcard every day to my children in the US and UK.