based solely on my experience, apart from the part about full speed (i really wasn't going fast, maybe 20 kmh but terrain was bad), yes.

If I include what fiancee sees on emergencies, which most people don't even want to know about but it's real life anyway, then wear it everywhere on bike.

you can see people getting quite emotional feeling they know what's best for them. Usually never had an accident, so it cannot happen to them. Whatever, I wouldn't push it, use whatever you want. But 1) you will cover all medical cost caused by lack of helmet in case of accident and 2) I would be cautious what to push on kids, but once people get emotional on the topic any discussion is over, as seen in this thread