what you are doing isn’t really cheating, it is actually an exploit. but since the exploit wasn’t what the developers intended, they made the 3 hour wait in between the upload/downloads.
as far as getting sent to the Cheaters Arena, that is for getting caught using apps to make Eternal Items & Pets that can’t normally be Crafted in DQ. as long as you know the limitations of Crafting Eternals, then you will know which players are cheating.
here is a Post that new players can use to know if an Item is hacked or not.
although i don’t remember mentioning in the post, Eternal Items can be found with Crystal Affixes, but only if the Eternal Item has an Affix that is on the Crystal Affix List. Pets can’t have Crystal Affixes, and only the Merlin Imp has Legend Affixes.
hope this helps.