The correct answer would be - it depends.
In northern places where boats get hauled out for winter you may find better deals towards the end of sailing season, the seller may be willing to give you a discount to save winter storage
costs. This may not be the case where boats are in the water
year round. More than the time of the year the price
may depend on the condition of the boat
and the reason the seller is trying to sell.
We bought our boat
in August, seller was desperate to sell as he had bought another boat so we got a little lucky. Before we bought our boat I had put an offer on another boat but the seller and I were off by ~1.5k so I walked away, this year he listed the same boat for 1k less than my offer. He could afford to stick to his asking price
as he owns a yacht club and doesn’t have to pay anything for winter storage
It really is different from boat to boat, that’s why I said it depends. I would find the boat you really like and then work
with the seller to find the best price that both of you can agree to rather than wait for that perfect “time”.