The size range you mentioned is accurate. I have an adult male here who is 8 ft long at 4 years old. I have seen some monsterous burms, though. I know someone with a 7 yr old female who is around 17+ ft and somewhere just under 200 pounds.
I love my burms and my retics, but they are definitly not for just anyone.
I have a suggestion, though. Why not adopt a rescue burm? You can get both albinos and normals in rescue and they really need/deserve 'forever' homes. That way, you won't be supporting the pet shops but giving some poor snake a good home.
[addsig]