Even if you take him outside still give him the d3 a couple of times a month just to ensure he is getting d3. unless he is going to be primarily living outside or outside most of the day I would not stop the D3. They can go outside at any age. The natural sunlight is great for them. Just make sure they have good shade(along with an area of sun to bask), water and protection from predators whether it be a screen cage, or you sitting there watching them. I live in florida and my chameleon is outside for hours at a time. It does get very hot here now with our summer approaching so I have to watch for overheating and I move him in the house to cool off. If you see your chameleon sitting with his mouth open outside while basking it is ok if it is for a very short, brief time. He is thermoregulating his body. If he continues to do it for any length of time then bring him inside if you have AC to cool down. When my weather is in the 70's and 80's he pretty much is out there all day long.