How slow can prepayment speeds go? No one knows for sure, but that question was the side buzz at the PricewaterhouseCoopers mortgage servicing rights conference held recently in McLean, VA. Many lenders are reporting slowing speeds, which is no surprise given the higher interest rate environment. Slowing prepays can hit the bottom line negatively since some lenders count on collecting prepay penalties, such as Saxon Capital, which reported less prepay income in the first…