Depends - if you ordered something and you are expecting it (and you didn't order it specifically as a Christmas present) then I probably would open it.Otherwise it can wait.The only exception to the rule would be if you ordered an expensive camera to take great photos of Christmas day. Then you will need the practice and you need to open it up...... Otherwise it can wait.
Open, open, open! :)you already know what's inside, so you should open and enjoy! :)
You're much better than me to have waited even this long!