I live in a small house. I try to purge my house of extra stuff at least once a year. I just finished the two bookcases yesterday. I have like 5 bags of books going to the thrift store and one box of books going in the shed.
I always keep a box in the trunk of my car. As I come accross things I don't need in my home, I put them in the box. When I have enough stuff to fill the box, I donate it to the thrift store.
I buy stuff from the thrift store too. I just bought an electric food steamer from the thrift store. I love it and will be keeping it. If I decided I didn't like it and wouldn't use it, I would just donate it back to the thrift store. If I spent $50 on it new, I probably would hang onto it because I paid "so much money" for it.