I regularly use some type of flasher tail light. I previously used a Planet bike super flash turbo. Periodically I would have to put in new batteries. I figured it might be good to be a little more ecological and try a USB rechargeable light. I found one last year that was nice and compact, good design nice and bright. The problem is that it no longer holds a charge particularly well and actually has gone dead while I am on longer rides.

I am wondering what experiences and opinions others have about USB vs batteries.