Oh gosh no we would never take the decorations and tree down on the 26th or 27th. We are still celebrating for a week after Boxing Day!
The tree and decorations and lights go up on the 1st, and come down on the 6th of January. We have them up for 5 weeks, and we love every minute. Every one of 10 homes in our cul de sac has Christmas lights up outside, and the whole road looks beautiful. 
We have friends and family around on a few occasions between the 20th December, and the 2nd January, so we wouldn't dream of taking the tree and decorations down as soon as Boxing Day.
Each to their own, but no way would they coming down the day after Christmas day. I agree with the people saying that the Christmas period is technically meant to be celebrated til 12th night/6th January...
Then again, we start celebrating it a week to 10 days early, by having a few meals out, and the works Christmas party, and watching Christmas films.... So maybe quitting it a week early is no different to starting it a week early IYSWIM.