While I am not so positive that atheists can't become theists, I still wonder. I've been an atheist for a long, long time and have no memory of ever having an "intensely atheist mind". I just don't believe. It is so easy anyone can do it.
My atheist mind is casual, at best. I can argue atheism all day long, but I put much more intensity into my work or my 3D drawings on my computer or into friendships and family. In comparison, my atheism is a blip in my life, energy-wise. I post here for fun, not reassurance, for instance.
Can you explain what an "intensely atheist mind" is? As per your testimony.
P.S. We don't have any Culver's out here in Montana. Do you deliver?