Having come from a motorcycle background with few 'retired' helmets (due to impacts), the approach I have started to take on the street is to wear a helmet on the roads that I know like the back of my hand - where I'm running at 8/10'ths. I happen to live right in the middle of some twisty rural roads with elevation changes............. the bad side being that it is all wooded, so you can not see through the turns. YMMV.

 

now I'm a 'member'......... I see the option - could have missed it before.