It depends on where you live and how you keep them. I live in coastal southern California where it is fairly humid. I have had a devil of a time keeping them healthy outdoors. They were always coming down with respiratory problems. Now, they have adapted pretty much, but it was only after I lost a couple of them. Indoors, it is dryer and they may have less health problems.
The females get a lot bigger than the males, and my largest female is about 8 inches long. I don't think they get too much larger than that. Maybe another inch or two.