I've used the HubBub helmet mirror for over 10 years, on day rides, week rides and a cross-country ride. The mirror is better than mirrors mounted on the handlebar or glasses frame. I've given it as a gift to friends, who enjoy it. I don't ride without it.
This is me arriving at work after a rainy ride. I ride over 6,000 miles a year and my Hubbub mirror is the third eye that keeps me safe rain or shine.