I've kept my female veileds at 80F for years and the males just about 85F... so slightly warmer...and the females almost always lived to be 7 and the males even older. They all seemed to be healthy as a rule.
For veiled females this along with a "diet" usually stops reproduction altogether...but they can be brought back into producing by increasing the diet a bit and increasing the temperature a couple of degrees. I never went any lower in the daytime temperatures because I didn't want to risk health issues...and they were good at those temperatures.
My Panther chameleons I kept a degree or two higher at the most. I worried that lowering them more so I stopped there.