I'll just stick with the "no helmet" at all for the time being. I'd much rather be comfortable and not feel like I am having my neck wrenched.
I wear a skull cap tied tightly so I dont worry about losing my sunglasses when I do an over the shoulder check.
I will wear the helmet for those days I commute this winter. It keeps the head warm. And I dont go over 50 miles an hour on my early morning commute in darkness anyway. I dont dwell on the safety BS all that much. I am a personal choice person as it were.