How often do you cull your collection?

Hello all. Been collecting now for 5-6 years. I’m approaching 300 records, and I find myself at an impasse. I can tell over the years theres quite a few I bought, just to buy, while a good chunk I actually value and want a part of my collection. My question to all of you is, how often do you cull your collection? How do you determine what makes the cut?