I am a firm believer in buying off season, from inventory and for us, close to the end of the year. The best week for purchases to me is the week between Christmas and New Year. This only applies to buying from dealers. Get the papers signed before the first of the year, but if you have add ons or changes, they can be done in January. Dealers want their year end figures to look good, inventory to be reduced and something off their books before the year begins. Floor plan interest is above 5%, that is their incentive to make a deal. Taxes are based on what is on the property at the first of the year. All things to your advantage. One more thing to consider, trade ins are a company asset, but not money. Businesses want money, more than assets.
All this only applies to items you really want or need, don't just buy because it is a good deal. The really good deal is being HAPPY and Satisfied.