I have a female Mojave who I bought at the 2012 Tinley Show (so 3/17/12), and since then she has not shed for me at all.
When I bought her she weighed 240 grams, and today she weighs in at 450 grams. She eats well, and did recently go into pre-shed for me a few weeks ago, but she didn't shed it. I've soaked her multiple times, her humidity is fine, and everything else I can think of. We have at least 15 other ball pythons as well as 3 blood pythons, all who have had perfect sheds and have shed multiple times within the amount of time I've had her.
When I bought her she did have what looked like a retained eye cap that we couldn't remove. It was just a white ring around half of one of her eyes. We were hoping she would shed it off in her next shed, but she hasn't shed. DX
You can sort of see it here on her left eye. I couldn't find a better photo of it.
http://i23.photobucket.com/albums/b3...s/IMG_8485.jpg
http://i23.photobucket.com/albums/b3...IMG_8480-2.jpg
After she got out of heavy pre-shed, it turned more bluish:
http://i23.photobucket.com/albums/b3...s/IMG_0472.jpg
http://i23.photobucket.com/albums/b3...s/IMG_0475.jpg
Her right eye:
http://i23.photobucket.com/albums/b3...s/IMG_0474.jpg
http://i23.photobucket.com/albums/b3...s/IMG_0485.jpg