Only during new seasons. I have a main theme i like, but i change it with holiday items or completely change it to correspond with the seasonal theme. Haven't changed it once until Halloween, and will decorate for Christmas and such
Once I have full sets of what i like, never really change it. I usually have one room that I'll change out for the seasons though. Spooky room will be Christnmas room next!
I change almost every week. There's so many different styles available that I just love to decorate with. Besides, what else will I do with the money. It's also just another way of not getting bored with.
I usually changed my house when I get a new piece of furniture that I like. I also change it on seasons like Halloween then it gets shoved in my museum.
I started out by just filling my place up with things I liked and then never changing anything...but last week I decided it would be more fun to switch my main room with each season / holiday set. That way I get to enjoy what I am collecting a bit more thoroughly. After I have completed whatever series I was doing, I can pack it up for storage and start on the next set!