I've noticed this as well - basically the reason is because DJ's are always trying to keep their sets fresh and "cutting edge" if you like, when doing promo sets (as you might hear on the radio). There's always a higher demand for a mix if it has forthcoming exclusives on, whereas demand would be less if the tracks were 2-3 months old.This may sound a little stupid but how come whenever song gets like month or 2 old, nobody plays it... they either play the newest or the classics..... any specific reason for this?
It's a philosophy I try very much to avoid to be honest - I prefer to believe that tracks are either good or they aren't. I think good tracks are timeless and still worthy of play once their novelty period has worn off - if they've been overplayed first time around though I might wait 6 months or so before reviving them