But you already knew that
It's a shame that most companies only get customers during the major holidays (Halloween, Thanksgiving, Christmas, New Years, Valentines, and Fourth of July) and that the big group is all essentially November to February.... What will you do the remaining 8 months of the year?
This is the time to set a hook for off-season sales. So, you only sell Thanksgiving items, but you over bought. Let customer's know that if they return after the Holiday they will find tips, recipes, one-offs, etc for your holiday. Don't pre-advertise any sales because you don't know what you over stocked, but do position yourself as an authority. Keep the customer's attention on your site year round and you'll have that customer again next year.
Christmas is the easy one to extend. With the exception of some truly specialized items, you can start selling in October and keep it up until April in some areas of the country. So the sled wasn't bought in December, if there's snow in the mountains, you've got a market. While I'm on the issue.... Some parts of the US don't have a winter -- don't forget to advertise your overstocked spring and summer items, southern families will thank you as well as those who are organized and know they will need that Hawaiian shirt in March but forgot to buy it last June.
Holiday sales, although it pains me to say it, are not for the holidays: they are advertisements for the rest of your year.
Oh, and by the way: I can almost see it now, Halloween costumes in vogue for a theme party on Friday the 13th, the Renaissance Fair, or for a full moon....