We went from Jan 7-14 this year. By that time all of the resort decorations were down, they go down around the 5th. All parties and activities ended Dec 31. The parade at AK was back to the regular one by the 11th (our first day at AK), even though the website had claimed it being the Jingle parade the whole week. The park and DTD decorations were all still up when we arrived. Everything was gone when we left at the end of the week. It was very odd going to MK two days in a row, first had lots of decos and the next day had none. Everything had been taken down overnight. The final day for Osborne lights was Jan 8th, so we did manage to get there to see that.
It was wonderful being able to see some of the holiday magic, even if it was after the new year. It really made me want to make a trip in December one year! But we are doing Halloween this year, so maybe next year for Christmas!