More often than not, I get random parts, very few complete sets. And when I do get complete sets, they tend to be ones I already own. But I also will simply not keep the set intact, and simply part it out. This parting out also happened to a couple of sets I got new (Mistika Tahu and Onua, the Hydruka and Stars Tahu)
I can change my mind on a whim. The most recent whim was to put together as many of those sets as I could. I was able to put together 16 sets, not all complete, but with the help of Bricklink, all are now almost all complete.
I had the ability to put together a couple more sets, but some important parts were used in some MOCs that I wasn't willing to take from.