Hell and God cant Co-exist.

[SteveII]

I seem to remember something about pigeons....

You've had millennia to think this shit through, yet all evidence points to a continual invention.

Continual invention implies adding new things. I do not think that is the case. 

Couple of reasons some doctrines might have changed over the past 2000 years:

• Advances in philosophy in general and philosophy of religion specifically.
  
• Advances in natural theology and its importance.
  
• Advances in our understanding of the universe and our place in it. 
  
• Decentralization of theological thought. Now we have many more sects and denominations that bring out variations in thought and prompt reexamination of ideas.
  

There are some doctrines that cannot be changed lest Christianity ceases to be Christianity (for example the doctrine of Salvation). The one under scrutiny in this thread probably hasn't changed much other than to fill in what it means and/or to articulate it in more sophisticated language.