A nice feature when cruising Princess, they have self service laundry rooms on the guest decks. The price was reasonable and sure saves from packing too much, its nice to know you can throw a load in any time and also nicer when you get home and don't have tons of laundry to do.
We did some laundry while on Coral 9/6 sailing and it was a huge convenience. Room contained many washers and dryers and never a wait. Iron and boards also available. Laundry was near the rear of our deck (Baja), just a bit of a walk from our mid ship room, but still managable. If you need coins, passengers service desk will make change for you.