Change things around often. Give a dig box but change the digging medium every once in awhile - compost, Yesterday's News, Bed-A-Beast, chopped hay, stones (large enough that they can't be ingested), shredded paper, a planted box with edibles etc. Add a pool for a few hours once a week. Put in a hammock, different hides, logs, rocks etc. for climbing and exploring. Toss in a stuffed animal, shoe, pillow, blanket etc. for exploration. Give him different kinds of feeders, hang some of his favorite foods from clips in his cage so he has to go after them. Take them out frequently, even out of the house and on trips around town. Play "fetch" with some worms (let them out of the viv, toss a worm and let them chase after it).
I have no doubt that beardies can get bored sitting in a tank all day long doing nothing but eating and basking. Anything you can do to give them a more enriching life would probably be appreciated.
