We were at BWI the first week of this month (April, 2016). We had no problem self parking. We arrived on Sunday, about 4PM. We parked in about the third row back from the entrance to the self-parking lot. I made it a point to look around and noted that there were at least 10 parking spaces in my immediate eyesight. I wanted to be able to report back, because I know people are concerned. When we left around 9am on Friday morning, there were lots of spaces available.
Having said that, once we park our car we don't move it again until we leave, so if there were more busy times I can't say.