Well, I used to kiss my kids on the lips, but it’s pretty rare now. The oldest two (11 and 7) outgrew it long ago. My youngest is five, and lippy kisses (as he calls them) are getting more and more rare. Sometimes when I’m tucking him in at night he will still kiss me on the lips, but he’s certainly starting to outgrow it. My husband and I both still kiss the kids on the cheek, forehead, or top of their head pretty regularly!
My family was not physically or emotionally affectionate at all. I really don’t know how kissing my kids on the lips got started, but I never gave it a thought until a question was asked about it here on Fluther a while back. We’re a more affectionate family in general than my family was, and even my husband’s distant relatives are free with the hugs and cheek kisses.
I don’t think there’s a right or wrong, just a comfort level that is going to vary from family to family and even person to person. The important thing is that each person’s boundaries are respected.