We do plenty of laundry on the ships. And, due to allergies to laundry detergents and the corresponding need to get all the soap out, for us each wash takes more than one full cycle :-( I try to pack clothes that can be laundered together so I don't have to worry about e.g. separating lights and darks. And I only use one washer at a time (well, unless it is 2 am and no other humans are around) so I am only tying one up for hours and hours.
A few tips:
Learn where all the laundry rooms are on your ship. THis webpage lists them and has lots of good info about laundry on the ships:
http://disneycruiselineblog.com/2013/01/onboard-self-and-full-service-laundry-and-dry-cleaning/
The laundry room closest to your stateroom may not actually be the closest or the best choice. Example: Our first cruise we were on the Dream deck 5 forward. One day I headed out to do laundry and our stateroom host saw me. He asked if I was headed to laundry and I said yes. He asked where, and I explained deck 6. He explained that the laundry room on deck 2 was actually closer/easier: walk to the forward elevators, go down the elevators, get off at deck 2 and it is right there. With the deck 6 i would have had to walk to forward elevators, go up one floor (stairs or elevator), then walk all the way back forward again. Deck 2 was half the walking. We used deck 2 laundry for that trip and it worked very very well.
The laundry room we used for our last 2 cruises was deck 9 forward, right around the corner from our stateroom. This worked particularly well for late night/early morning laundry.
I always set a timer or alarm on my smartphone for several minutes before the cycle should end. This lets me get back to the laundry room before or as it is ending so I can rescue my laundry. That said, I have not had the experience others have with people removing other people's laundry. I HAVE seen people leave their completed cycle in the machine for hours and hours.
I have done laundry during late dinner -- just nip out and switch the cycle and then come back. This worked better using the deck 2 laundry room as it is a quick walk from all the MDRs.
We bring our own liquid detergent - one of only two kinds I have found that we can tolerate. I bring a couple Nalgene 250 mL bottle full of it and a small measuring spoon (the amount needed is measured in teaspoons). Although the Nalgene is leakproof, it still lives in a double Ziploc to be safe, especially during travel.
For allergy reasons, my first laundry cycle any time I do laundry in a public washer is to take two towels (pool towels are handy for this on the cruise) and run them through with just water, in the hopes that that cycle will get any excess detergent and such out of the machine before our laundry goes in it. Unfortunately, it means even longer to do the chore.
Finally, I bring a Scrubba Wash Bag (
https://thescrubba.com/) so I can handwash some items in the room (e.g. bras) either because they shouldn't go in the washing machine or so they are done quickly. The challenge with it is drying anything in those staterooms can take a long time.
SW