My hobbies tend to be full of experimenting with things. For instance, I buy a lot of games for sales and end up playing through only a portion of them.
With that said, I've noticed that I have a similiar approach to collecting toys. I have a lots of toy lines I have gotten a bit into but have not collected that much. Though I usually try to get some kind of logical collections finished. Like from DCU I have the main Justice League characters, and from Turtles I have the turtles themselves.
I have also sold two collections - My Little Ponies and the original MOTU. The reason for selling them was mainly space issues. The MOTUC and Marvel Legends collections take a lot of space and on top of those I have lots of figures from other toy lines.
Now that I think about it, I do not regret any decisions I've made. I mean, I am pleased with what my collection is now and what I'm focusing my resources on at the moment (mainly finishing MOTUC).