Rapper M.I.A. is a little young to retire from performing live, right? Music tradition says she’s supposed to kick around for at least another 10 years until she even thinks of retiring, and even then, it’s only so she can launch a comeback tour a year or so later. That’s why concertgoers at Tennessee’s Bonnaroo were shocked to hear M.I.A. say she was retiring from the stage not once, not twice but threeseparate times during her performance at the 2008 festival. Claiming she wanted to focus on recording new material, she was, um, MIA for the rest of her tour, canceling dates in Britain. She’s already broken her pledge, performing — pregnant, no less — during a Brooklyn, N.Y., party and the 2009 Grammy Awards. Expect that comeback tour any day now.