Christmas != red hat/suit
So, red hat/suit = it's over when "Christmas" in terms of presents and family and red trucks delivering drinks is over. Since this Christmas isn't really serious anyways, you can easily be "funny" by wearing the hat whenever and throw presents around in green/red/golden colors.
Real christmas = ends with New Year, Epiphany takes over (for Protestants; check your religion and its liturgical year if you are into it)

A radio station I listen too still has a icon showing on my car's dash for Christmas. been thinking they should change it for a while now, so assume same for this question.

Its your Avatar man. So what ever you Like with it.

Whenever you want

change that ish now

3 kings day is on the 6. Those were the guys that supposedly brought gifts for baby jesus.

There is a saying in Norway, Christmas lasts until Easter

Read the following as a guideline and not as a hardrule.
Simply the day after christmas, then you go for a winteravatar.
The real problem is when do you start with a christmas avatar for me as dutchy its quite simple 6 dec the day after sinterklaas, maybe for the muricans after thanksgiving.

welp