My female panther/pictus was 3-4 months old and my male was 2-3 months old, I put the female into the males tank so i could clean her tank out, and they mated, I didnt even know their genders at the time. a few days later the female laid her first egg.
The female didnt come out of her moist hide(where she laid the egg) for about 3 day/nights straight during her egg laying, so I think that might be an indicator that she had a hard time passing it through, she weighed 7 grams after laying the egg. I dont know if the egg is fertile or if her laying it had anything to do with her and the male mating.
So as far as how old they have to be to be able to "do the deed" and produce an egg is about 3 months. As far as, is 3 months old a safe age for breeding them with out the risk of killing one of them, I dont know, but I wont be taking the chance again and I plan to wait until they are about a full year old until they are reunited.