There is no end. I just found out yesterday there is a desert chameleon that lives in the sand. Got to get one of those bad boys for the climate down here.
I usually just let them decide. Only enough crickets for them to take out the majority in an hour or so, and then I just hand feed as many worms as he'll eat. He usually gets bored pretty fast once he's full.
Just wait until their entire body is covered in a paper mache like coat. It's the coolest thing ever. My guy went and scratched off a big part of his side like a dog scratching an itch, pretty cool.