Yeah, with the hay ball, I only hang it for a few days and then take it out for a few weeks. Otherwise my tortoise would probably lose interest in it, but every time it is reintroduced it still seems somewhat novel to him.I've had limited success with brushes attached to the sides of my outdoor enclosures for self scratching as well as balls made of something unchewable and large enough to not present a any issues. Both of thos had a lot of initial interest, then eventually none at all.
The best enrichment that is a constant is placing food in areas where they can look for it and places to hide and wonder around.
Of course this is much easier with an outdoors enclosure of a hundred or more square feet.