Diego is spot on, you could pop the array front (delete 1st, then display second, etc.)
A couple other options:
1. Destroy the first one when creating the new.
2. Opacity lowered for old (or both).
That's the nice part of programming, whatever you want is perfect.
Just adding, recall the old super mario brothers. It spawned messages at point x,y then move up all the old with a fade. Was kinda neat.