I typically will throw a male in with the females once they get to around a year old, but sometimes I put it off until they're a bit older.? I think their diet and overall health are far more important than any number (age or weight).
You have to remember, these animals don't have anyone separating them in the wild and just about anything goes.? One thing I've learned with reptiles in general is that Mother Nature knows what she's doing.? ?Males probably won't breed a female that isn't putting off pheromones that tell him she's ready, so I don't worry about age/size too much anymore.? Once they're a year old and 30-35 grams, I'll pair them up and wait for eggs.? If they're fed properly, they all do just fine.
Thanks to you and Martin for describing in better words what I was trying to say. I agree overall health appearance and diet are the most important thing. All the geckos I have put together for breeding are of an unknown age so I went on weight, but mostly appearance when I put them together. As a first time breeder of cresteds, I am erroring on the side of caution, instead of putting them together to soon and running into potential problems down the road.