First I am quite frankly suprised both of them are still alive if they are truely one year old.
One veileds are extremely aggressive species not only to each other but towards their owners in alot of circumstances. Chameleons have hollow bones and are capable of breaking each others bones in one clean bite. They usually go for the jaw or leg. Again one clean bite to the jaw means it is broke and they will die.
Two it would be impossible to control the breeding. Male veileds have been reported to rape immature males of the same species. It is thought that they mistake the undeveloped colors for that of a female. While I have never actually seen it written any where I would have a hard time believing that they would not rape a female assuming she could not escape. I am also unsure if a female would even lay their eggs in the presence of a male.
Third would be diet and supplementation control. Females require a little more supplementation and a little less food during their lives. Controlling how much they eat can lower the clutch sizes which in turn could extend their lives. Since females produce eggs they will require more calcium. With both in the cage it would be very hard to control who gets what. Some keepers have successfully kept their veileds from even producing eggs.
Forth is the stress factor. Stress will lower their immune system. So now not only are they stressed but their is twices as much feces, bacteria....etc.. in the caging enviroment. Leaving them wide open for an illness.
Fifth is the cage size. Now it sounds like he does have a big cage but not really. Males are very territorial. They will roam and claim as much area as they can. For you to give both enough room to establish territory, enough room for them to hopefully respect the boundaries I think something like a medium sized bedroom would be in order. Densely planted, perfect humidity, multiple basking areas....etc... It would be far easier, cheaper and more efficient to cage them side by side with a divider so they could not see each other. Even in a big room you would still probably run into all the above problems. There are more but tired of typing.
