ProSites Configuration - Free Blogs

I'm obviously missing something really simple. I want members to be able to join and select a single blog during registration. From there they'll have the option of upgrading to a single premium account with new theme and plugin selections.
I've removed the pay to blog option yet blogs still expire after being created. See here:
What steps do I take to allow creation and access of the blog without going thru Pro-Sites? Or does it not work this way? What am I missing?
Any responses appreciated.