In hip hop, your sound isn't youthful or old school; It has either changed to fit current trends or it is a flow from a previous era. Sometimes the most successful rappers adapt to what the youth sound like; like Kanye. Other times, rappers get successful with an old school flow on new instrumentals; like Juicy J. Sometimes you have artists like Lil Wayne that lose their connection to their market by missing key components to their appeal: truly comedic punchlines he laughed at in the take he recorded, his massive sense of confidence, or instrumentals as good as "Tha Carter 3".