As a kid, Mom kept the tree up until Little Christmas, except if the needles were dropping too fast.
I'd keep my artificial tree up all year if I could. One year I was well on my way, changing the ornaments to suit the Holiday (ex: red white & blue for July 4). But the house went up forsale in the fall and the realtor made me take it down.
Now I have a small (30") half tree that hang on the wall in the sunroom and it is decorated with miniture lighthouse ornaments. It does stay up all year.
Gotta love Christmas!