For years now I've been carrying a spare rear light, Fibre Flare, checking it regularly, replacing the batteries, keeping it in tip top condition. Today I used it ! Thought I had checked the Exposure Blaze charge level last night, green power button, but apparently not, it wasn't flashing 1:15 in when I looked back. Bit of a bummer having to stop spinning, and no idea how long I had been riding without a light (glad I recently put some reflective tape on the mudguard). If the Fibre Flare hadn't worked I have a second spare Knog USB blinky light which I keep topped up (also have 2 spare front lights that I always carry, and never use ...)