the usual collector/hoarder mentality, I have so many copies of certain books its not funny, if I see it cheap i buy it, EG some Heinlien paperbacks, I have 6+ copies of, all the same, but if I walk into a thrift shop and see Stranger in a strange land for 50c I CANT not buy it. Get teased by my daughter endlessly, and its silly cos it takes so much space. With Posters, I originally found it very hard to let any go, now I stick to keeping my core collection, and the rest I can let go of (sometimes).