Yep, I believe it can happen at any age too. Sebastian knows when I'm not there. In fact, he will be screaming his head off while M has him for a while if I go out, and then he'll stop the minute he hears me come in the door. I'm trying to get M to spend more time with him while I'm in the house so that he gets more used to him too. I think Jodi's suggestion is a good one!