I learned long ago that if you can't display your collection and instead it sits boxed in a closet or in storage or in the attic, then you're not a "collector" but a "hoarder".
Get rid of the "stuff". You're getting no enjoyment out of it. And don't fall into that trap of justifying the hoarding by thinking, "One day I'm going to buy a bigger house..." or "...one day I'll convert the baby's room into my Man-Cave..." Even if it does happen, you're tastes and hobbies may have changed by then.
I've always been selective in regards to the pieces/items that I buy. With that in mind, I have sold off very few pieces. Those that were sold ended up going for significantly more than I paid for, allowing me to fund my hobbies more affordably.
But to be honest, my "hobby funds" have been going in a different direction lately.
Oh and...
I'm selective because I refuse to sell and space is at a premium..
Money isn't really an issue for me.