My kids weren't into silkies, but elder dd has a stuffed lion (named, appropriately enough, Lion) that she's had since she was born. She still sleeps w/it every night and we can't go on any trips w/out it. We once accidentally left Lion in a departure lounge in the airport in Toronto....talk about panic! She'll be 12 in December. Younger dd (9yo) has a blankie w/fringies on it that she loves. Same story....still sleeps w/it every night and wraps up in it when she's feeling stressed. I wonder how much of the attachment is a conditioned response, though....child feels stressed, we give them <insert object here>, they get over feeling stressed (as they would eventually anyway) and they come to associate said object w/stress reduction....
Just wondering.....