I haven't the last two years, but that's because two years ago I went for my first appointment and then the rest of my benefits (and cash out of my pocket) went to getting my wisdom teeth taken out. Then this year I went and was going to go back to get a cavity filled, and literally three days beforehand I ended up fracturing the tooth, so then I had to go use the rest of my benefits (and cash out of my pocket) for a root canal. So both times, with no benefits left, I skipped the second appointment in the year.
Hopefully this year we will have no major emergencies and I will be able to go twice. =P Normally I do go every six months for a cleaning.