I know to ask "Where did that come from?" Now, she's self-aware enough to tell me. Not so much when she was 2 or 3, though. She would use whole chunks of language (phrases, sentences, or even more) contextually-appropriately, but I could often identify where she got them from. (Books, TV shows, conversation, the radio, etc.)
DD3.5 has been doing this type of delayed echolalia since 21 months old. However, like your dd, it was always intentional and contextually appropriate. She was always aware what she was doing and could tell even at 2, where the dialogue came from. I believe that this type of repetition helps with language acquisition and is nothing to worry about. Based on my research, echolalia that is involuntary and done without comprehension is something to worry about, but especially in children >5 yo.
Jolaine83, you can either wait to see if your ds outgrows this in the next 6 months. Or if you are really concerned, talk to the pediatrician. Hopefully it is just a phase.
