Personally, I don't use AB stuff to gain a certain headspace. It's not about regression really, more self-expression. It lets me connect with my innermost psyche, and in doing so communicate more directly with the emotional reasoning that drives me.
Truthfully, I'm a little boy at heart, and my adult life builds on top of that. Without being AB, I have no way of having an internal dialogue with that fundamental part of me. Without that dialogue, my emotions will get the better of me. I will not be driven to succeed in the ways I want to, because I will not develop the emotional strength to be so disciplined.
I'm a strong believer that from emotion comes action; thought comes later. You may know how you should react to a situation, how you should behave, but you will not do that unless the emotional backing is there. For some people, this comes naturally. For me, it does not. My emotions are a tangled web. It seems the only way I can comprehend them, get to the core of my issues, and resolve them is by being little. That's what I hope to achieve as an AB.