ALWAYS, but I'm down to a Scorpion half-helmet due to neck issues.

Fellas, I drove Rescue for years. I saw too many minor bike "drops" turn into a cerebral bleed. If they get the $7000 helicopter ride to a trauma center and get the pressure down with a drill-bit to the skull, they may be ok. I've seen grown men crying and arching their back as the pain in their head from the pressure build-up became unbearable. I've seen beautiful women with partial paralysis (stroke) from a minor accident. Wear your helmets.