Originally Posted by
pdlamb
Two lights is good even if you have a dyno (steady) light because sometimes the connector works loose. The second blinking light keeps you lit when that happens.
And of course a third blinkie keeps you lit when the batteries on light #2 are flat. And ...
Another way to deal with occasional failures is to determine the root causes and make things more reliable, where possible. My dynamo powered headlight has proven to be reliable enough for me that I don't need a backup. I need to improve the connection to my tail light, however.
I'm thinking of carrying a small light for things such as roadside repairs, as a dynamo headlight isn't useful for those.