A young dragon needs a lot of protein because they are growing very quickly in a very short period of time. They get this protein through large amounts of live bugs on a daily basis. Once your dragon is an adult however, they are no longer growing and they don't need nearly as much protein. Too much protein and fat (i.e. bugs) in an adult dragon's diet leads to a fat dragon, fatty liver disease, and other health problems. This is why a young dragon's diet is 80% bugs and 20% veggies, but an adult should get only 20% bugs and 80% greens and veggies. An adult dragon should get 30-50 live bugs a week (30ish if you're dealing with superworms, 50ish if you're using mostly crickets, most other bugs fall somewhere in between), and a large daily salad.
The age of adulthood varies depending on who you talk to. At 12 months the majority of your dragon's growing is done but they do continue to grow and fill out until they're about 18 months old. In my opinion, at 12 months you should start slowly weaning your dragons back from the live food and increasing their salad intake so that by 18 months they're on the appropriate adult diet.