I have one that's almost 2 and I just leave it in the enclosure and it will eat one every 1-2 weeks. I read somewhere that they will really only eat them when they feel like they need calcium. Maybe add more calcium to its diet and it won't eat it so fast??
If he eats the whole thing right away, I would give him one only every two weeks or more. As long as he has a good diet and sprinkle calcium on his food about once a week, you can hold off longer on the cuttle or don't give it at all. You can even sprinkle the cuttle over the food instead of giving it too them.