Not many folks want to hatch in winter, but there would be no harm in advertising them.
HOWEVER, please consider the following points before offering your eggs for hatching:
1. Early eggs often have many more problems than mature eggs during incubation. As a result, you should never set nor offer for sale eggs from ducks who recently started laying. You should give them a minimum of about three weeks before you think about hatching.
2. Most responsible sellers only offer eggs that have been tested for hatching. Which means you have to run a test batch before offering for sale. Alternately, you could partner with someone who wants to give it a shot at a very low cost & understands that they haven't been tested--you sell them the eggs at half cost or less in exchange for the agreement that they'll give you feedback on how the incubation process goes and how many hatch, health, etc. Once you know your eggs are good and healthy for hatching, you can start selling at full price.
3. Finally, even with strong mating behaviors, winter eggs are often infertile. Before you even try incubating, you should do some spot checking for fertility (pictures & help with that available here:
https://www.backyardchickens.com/forum/viewtopic.php?id=16008). If fertility is present but at low rates, make sure you let potential buyers know that and include a price break.
4. Even if you don't hatch and/or sell this winter, it would be a good idea to run a test batch a few weeks before selling season in spring before you offer eggs for sale.
Good luck!
