I brush and floss three times each day. On the last flossing of the day, I coat the floss with Listerine.
My dentist advised twice per day flossing (I used to do it once) to prevent bacteria from getting under the gumline and eventually eating away at the bone. They took measurements and noticed some erosion of the gum line.
I got myself into the habit of three flossings per day. A bit obssessive perhaps, but I'm extremely kissable now.