The squishier the saddle, the more likely it is to chafe and pull and otherwise be miserable on your soft parts, and the longer the ride, the more that's going to happen.

I went from a Lithia to a Jett, and while it's not perfect for me, I'm MUCH happier with the firmer saddle.

I don't really have any advice ... I would think your sit bones would be plenty tough with the mileage you're logging; mine stop bruising with much less. But I wonder how often you're riding the longer distances and if it isn't just a matter of more longer rides?