London - After being Simply The Best for four decades, Tina Turner has decided at 60 that it is time for a rest. "There comes a point where it is just undignified to be a rock'n'roll star," said the American singer, who has just recorded a new album and is ready to embark on what could be her farewell tour. "I want the tour to be the biggest and the best because it is going to be the last . . . I want to go out on a high," she told Britain's TV Times in an interview.