We've been using these for our son from 4 months til the present (8 months old)", and we love them. They work well (tested on my own ears) and yet are comfortable enough that he doesn't try to get them off. He's even fallen asleep with them on!
Taken him to movies, concerts, and even phantom of the opera. Phantom is a loud stage production but he didn't even flinch - and even fell asleep!!