Originally Posted by coominya

For someone who only rides in the dark every month or two the cheapos probably make more sense.

Originally Posted by cyccommute

They make a lot of sense for someone who rides every day as well. With a $20 light, what does it matter if the battery shorts out? By another light and it comes with a battery. It also makes sense from the standpoint of having more than one light source. Not just for back up but also for utility. Multiple light sources make you stand out more and, at $20 per light, having two or three lights (a light on the helmet is extremely useful) doesn't break the bank.

Originally Posted by noglider

I read here on BF the suggestion to carry a backup light, so I did for a while. My thinking is that my dynamo-powered headlight could fail, leaving me without a headlight. I try not to carry anything I'm unlikely to need. I don't carry spare spokes or spoke wrenches because while I have broken spokes on the road, it happens infrequently enough not to justify the trouble. And when it happens, I can deal with it. I can also deal with riding with no headlight if I have to. I've been riding with dynamo-powered lights for over three years now, and the failure rate of my systems is low enough to show me that I don't need a backup headlight. In three and a half years, I have had two failures: 1. one wire came out of the tail light. 2. While my bike was locked in public, a vandal tried to steal my headlight and failed. He bent the mounting bracket. The light still worked. After I got home, I bent the bracket back into the original shape. This really shouldn't count as a failure. So my headlight has failed zero times in three and a half years.

I cannot perceive the drag the hub creates. If I get home tired from the effort of my ride, I cannot rightfully claim that without the hub, I wouldn't be tired.

Originally Posted by Walter S

Yeah, IMO a dyno is reliable enough that you don't need backup. I put a shymano hub dyno on my bike in October 2012 and I continue to use it problem-free nearly every day. I keep it turned on pretty-much 24x7 as I think enhanced visibility in shade/shadows might give me a wider berth on the road - anything to draw attention and wake up the day dreaming drivers.