So when would the expiration date be? How long before the new gets put in the old bin? You gave no practical answer at all. Try re-reading. Or better yet, email the OP and see what his definition is, it's his thread not yours.

What is current music? Something that came out in the last month, year, decade? If you look at the big picture "current" could very well mean during the last century. And just because something was put out recently doesn't mean it's "current music". It could be reworkings of old tunes or plainly unoriginal recycled music or new releases of pre-recorded songs from years ago. What is truly new today? Would that be the correct definition or something that's got a copywrite of 2010 on it? "Current" has about the same ambiguity of Classic Rock and what somebody considers current may be completely stating a misnomer.