The reason some say don't wash is that eggs have a natural coating that prevent most germs/bacteria from entering the egg. Washing will remove this coating. The reason some say wash is because they are dirty and germs can still get though particularly if the shell is defective or cracked.
So the options are: wash and except that you get a clean egg with less natural protection,
Don't wash and except that you will have dirty eggs but with more natural protection,
or wash right before using.
There have been lots of various tests determining how long washed versus unwashed eggs last but unless you keep your eggs more then 3 weeks it probably won't make any noticeable difference. Check here for suggestions on
egg washing for the backyard flock.
Personally I wash (hot as you can stand water is usually recommended if you do wash), wipe with vinegar, then wipe with a paper-towel with a tiny bit of oil on it (just a teeny bit to help the shell not be to porous), then refrigerate. It works well for me but I know others are happy doing it other ways. I know that most agree on if you do refrigerate them then don't take them out and let them sit on the counter. By the way the sponges with the green scrubby side are awesome for cleaning eggs if they are really yucky like when some silly duck decides to lay in the middle of a mucky spot. Most say don't use soap or soak in bleach, some could be absorbed. If you do want to use something more then water then I suggest buying a product for the purpose such as some of
these . Check/shop around though as the egg washes are available from various places.
If you can get your ducks laying in a nest box it really helps. Fake eggs left in the nest helps out. I found that lots of bedding seems to help keep the eggs clean, the box used, and prevent breakage. I do have an egg laid in the middle of the yard now and then though.