I can offer my experience with collecting adiction. I was collecting Lego models. Starting in 2000, I had all the UCS (Ultimate Collectors Series, the most detailed and huge Star Wars models). I had every UCS model that was out there. Then started collecting modular buildings (great looking buildings, with intricate details on them), then normal Star Wars models, Lord of the Rings models, Winter village models, Egypt adventures models. It became too much. And when I had all the previous models, it was impossible to miss any new one, I would be missing it in my collection. The space for the models became problem, as well as money for it. So I decided to sell my collection - most of the pieces I sold to private Lego museum, the rest (mostly normal models, not UCS) I sold elsewhere. I learned, that when I did not have the previous models, even though I like the new models, my need for the new models is lowered. I just told myself, why buy this one, when I do not have previous ones. Bought new car with the money I got for Lego.
Then I started collecting statues (PF, 1/5, 1/6, 1/7). I know I am very limited with space, so I choose only statues that I really like. I have similar fetish I had with Lego, wanting all the existing statues in MOTU series (first Sideshow ones, now Tweeterhead, plus PCS Battlecat), but in SW I really stay with what I like and must have (such as some of the Mythos - Vader, Ventress, Maul). I think the only way to keep it down is to have given space for the statues and really choose what I need because it will take the valuable space. When no more space, choose which to sell and replace it. Not to buy new showcases for new statues, but keep limited "space budget" that will not allow you to get the collecting problem grow too big.