Generally around the time you put yours up.
Well.
For us it's almost December. If I put mine up after Thanksgiving it would already be up.
We have a fake tree. I hate real trees, they smell awful (if I wanted to breath pine tree 24/7, I'd live in a forest thank-you, I can find those year round), they make a horrible mess and you always have to get a new one. Plus fake ones are so much easier to put away. And they're not as puffy, so you can actually put the ornaments on so you can see them, more room for presents underneath.. and you can put up as early as you want, and put it away when you want.
I would be the perfect poster child for fake Xmas trees.