In the Upcoming Halloween Update Posted By SOOPUR SELL (supercell), there have been sneak peeks released showing new skeleton traps for TH 8+. I also remember the Santa Strike from one of the Christmas Updates. My question is when these holiday events finish, do we lose the money we spent on the Traps or do we keep them forever?
Yes, obstacles stay indefinitely, and are worth the same amount in the future.
So, you can keep them around for decoration, without losing anything.
Source: I've seen my clanmates keep Christmas trees forever, and I kept my second one for months before it got in the way of new buildings, then I removed it and got the same amount of gems.
edit: Misread the question - also, this particular Halloween trap stays forever, according to their update notes.