With the newer USVisaScheduling system that they started using in October, I don't think it locks you out anymore. It is pretty fast and before my second interview, I was checking 5-6 times a day without being locked out.
Interviews typically show 2 or 3 months out. For my first interview, I scheduled it in mid September and first available was early December. For the second interview, I scheduled it early December and first available was early February. I was lucky and after checking many times, found an available date in mid December and changed the second interview to that.