My DD still takes her "mermer" blankie to bed with her and I'm fine with that.
She's had it since she was about 7 months old but I wouldn't say she became really attached to until she was over 12 months.
It was especially good when she started daycare - she could take it with her and she found tremendously comforting and it really helped her sleep while she was trying to settle in.
I'm all for comfort objects, if it makes them feel better why not?