Speaking with my 'radio' hat on - air play for tracks becomes less likely as the tracks become longer... between 3 & 4 minutes should get air play, but anything longer than that is likely to be rejected because we only have a fixed amount of time to play as much variety as possible!

A lot of modern stuff tends towards 6 or more minutes, especially young instrumental bands! That means we could play two three minute tracks instead... or fade and talk over the rest of your track... sorry!

Make sure your CD insert has the track timings on it, too!