I rang Auspost the other day to ask. I was told "Well - it normally takes 7-10 days, but with it being Christmas I'd send them now"

Incidentally - shipped a parcel by sea to the UK on the 29 September.
Arrived 2 weeks ago!

Surface mail takes longer than to ship all your worldly goods around the world for some reason. Last time I used it I saved about $4 and it took 2 and a half months