but accessories CAN downgrade, they will not get deleted, but get down, also you loose the upgrade item, so on a TRI Ogre, the ogre ring +0 is gone and it CAN go down from DUO to PRI.
But I tested it with Witch earring and lucky, they did not go down.

Best used for cheap blue gear like mark of shadow, witch earring, Pirate accessories or for armor/weapons, because they dont scale up 1:1, like accessories.
If a Ogre Ring cost on PRI 200.000.000 then you need 200 crons, but if a weapon cost that much, you don`t need the same amount.
my DUO Grunil cost max 45M and I need 21Cron stones to protect it form failing.


Also best use: Save them for T9 trys you need 100 to protect the fail, to just loose 50% of the used mats instead of all.
If you pay like me 350M for 100x Stonefodder, then the 100M for 100 Cron stones are nothing