Just to add to this: There seems to be an unspoken consensus about the relevant ratios of A to D3 (I think it’s 10 parts A to 1 part D3). I cannot comment on whether these are principled, but they exist. And whether this ratio is correct for chams, the literature suggests that each needs the other. On the other hand, there is literature supporting an antagonistic relationship between A and D3, but if memory serves, the antagonism only goes one way. I’ll have to look it up.Actually, utilizing D3 once a month can work for a jackson's chameleon. It also depends on the number of feeders dusted and the potency of the specific supplement. Reptivite w/D3 has worked well for me on a once a month basis--dusting only two feeders. With that said, reptivite contains more D3 than repashy LoD--however, I know of people who use LoD once a month as well.
Just recently, I decided to split up my once a month D3 regimen into twice a month, but only dusting half of the feeders in D3 and dusting the remainder in plain calcium. I figure splitting up the D3 into two smaller batches would be healthier for the body.
As for the statement that Vit A should be used more frequently than vitamin D--that isn't really true. But I guess it also depends on what type of Vit A we are talking about. Proformed Vit A (beta carotenoids) can be given more frequently than Preformed Vit A (retinol) simply because most chameleons either have natural safeguards for Proformed A or simply do not utilize it (still debated). Preformed A should be given in moderation as it can cause edema as well.
From my research, Vit A is an incomplete antagonist to Vit D3. While I don't really understand the science (yet), you should really be giving D3 about the same frequency as giving preformed A.
Long story short, A and D3 have a relationship such that each needs the other, which is why they are typically given together. But too much of one may inhibit the other, and the default appears to be A to D in a 10:1 ratio.