Maybe you could start by challenging yourself to wearing every shadow at least once in a month. If you don't like a shadow when you put it on, out it goes? Maybe try getting down to just the 30 palette first and see if you use that more (but keep the empty 15 in case you want to get down to that)?
Going slowly will decrease the risk of regret that you tossed them and the need to run out and buy more to replace them.. If you find you have several of a certain shade ex. 5 transition colors or highlights for example, and you only use the same ones all the time, maybe you could get rid of your least favorite ones?
One thing I did was put 4 shadows in a quad and use that for a week. Then rotate the colors out once a week for different ones from your larger palettes! Keeps your selection small but you still end up using more of your collection. I found tossing 1 or 2 every once in a while was less painful than culling a bunch at once, but do what feels right to you!
Hope that helps! Let us know what you decide to do!