Tradition....

My parents tree is decorated with gems that are as young as last year, and as old as I am and all in between.
Each year, mum would give my brother and I a decoration for that year, and one for their own tree too. When we each moved out, we took our decorations with us, and then started to add to it ourselves.

The other tradition shown here, but hard to tell on a quick glance is, that is a candle on the tree, not a fancy light.

We still use candles on the tree for Christmas Eve when we do our gifts. Only twice in over 30 years have we had to forgo because the tree may have been too dry. We usually only get it a few days before that night, so it's as fresh as can be.