Madonna (inset) may not be the most relevant of singers anymore but she is still selling out big tours, filling arenas and selling records. She is getting top billing at international awards ceremonies and events. Her continued presence among the world's top-selling artists is thanks in part to her capacity to push the boundaries. It's equally down to her judgement of when to stop pushing them. Which is a lesson she could teach Miley Cyrus (left). The former Hannah Montana star has established she's a promiscuous bisexual and has done so many nude photo shoots that the last one needed a live pig to gain attention. She's 22. It's time she learned from Madge and cooled her jets for a while.