Thanks, got it.

Once you build it it should remain in game until you deconstruct it. The item should disappear from the construction menu with the next patch likely in a few weeks.

Once you build them, they stay put, but after the season is done you can't build any more.

Which reminds me to build that Christmas tree forest while I can.

You could still build it with console commands, which is what i usually do. I disapprove of seasonal items which come and go every year again. Just collect the items, throw them on the ground, removedrops, plant a tree or maypole.

there are a christmas/winter group, a halloween group, and a spring/summer group that I know of?