When should you sell Treasury Debt?

I have more than a few economist colleagues who lost money by betting that long term treasury rates would increase and the dollar would fall.  We know this will happen, but we don't know when:

Dan Fuss, who manages the Loomis Sayles Bond Fund, which beat 94 percent of competitors the past year, said last week that he sold all of his Treasury bonds because of prospects interest rates will rise as the U.S. borrows unprecedented amounts. Obama is borrowing record amounts to fund spending programs to help the economy recover from its longest recession since the 1930s.