ib4 charge spoon = jesus

I'm guessing your bone structure is a lot like mine. You probably have very wide sit bones. There have only been two saddles that don't leave me with those feelings you describe and that's the Charge Spoon and Bontrager Inform RXL in a 154mm width. Look for something with a flat back section that is wide. I don't know if any saddle still feels like heaven after 20 miles but with a combination of good padding and a well fit saddle you should be able to pull off some longer treks.