I couldn’t agree more. My gravel bike is currently set up with IRC Boken Plus and orange seal endurance. I can literally go 2-3 months without touching the tire and the pressure and sealant remain the same. My road bike on the other hand has the same sealant, but Vittoria Corsa Pro TLR.
I need to check the pressure a couple times a week. I chalk it up to the cotton sidewalls. They just don’t hold air as well as the indestructible IRC.