[Nicolas Gauthier-régis]

For those who are still looking for an answer or an alternative, here’s my suggestion.

In AfterEffects CS6, you can select all your layers and : Right Click – Keyframe Assistant – Sequence Layers

Then you can order your layers in the order they’re placed in the comp and you can also overlap them. Letting you add a 15f before and after each layers. This tools also gives you the opportunity to automatically put a fadeIn and a fadeOut.

Cheers!