In the Catholic tradition, Christmas decorations are usually put up for 40 days.
From Christmas Eve until the Purification of the Blessed Virgin Mary, Feb. 2.
Of course decorations are gradually taken down, as the tree dies and the Christmas flowers or pine bows wilt, etc.
It is nice to leave the manger scene up until the end.
In many countries, such as Italy, while not every family had a Christmas tree, every family had its own Christmas manger scene. A creche with figurines. A nice tradition. Each year new figurines can be added. The carpenter in the family can build the creche.