I recently broke down a large tank that had mineralized topsoil with oil-dri as a cap. It was running about a year, no major issues, just did a big changeup. Since I still had a screen setup from sifting through topsoil, I ran the year old oil dri/mud mix through the screen and the oil dri rinsed clean in a few minutes and is still holding its granular shape.
Ended up putting it in a new tank.
Clubs are lame Club #1