In keeping with the opening post: It can't hurt to have the rear reflector as a back up. That said I don't use one on mine. Like others I use two rear lights. My main rear lamp is so bright that all I have to do is turn my head and I can see the plume or the light reflecting off signs. If I use a helmet mirror this is even easier to do. I also use a light on back the helmet. ( *note my main rear light has a remote switch that sits right where the seat post and top tube meet. ( *Xeccon Geinea rear ) If the battery is low it will give me an indication with a "red" warning led. It is very easy for me to see at any time. ) The rear helmet lamp cannot be seen unless I have a helmet mirror on. With helmet mirror I just hold my hand up to the back of my helmet and I can see if it's working.

Right now I have no good place to mount a rear reflector. I plan on buying some "Reflexite" tape at some point and mounting some to either the seat post or my lower rear fender ( if I'm using them ). In the mean time I always ride with reflective bits on my clothing and shoes. If by chance both rear lights went out I would not be invisible to approaching traffic. ( I also sometimes use wheel lights which are also visible to traffic approaching from the rear ). Still, all these things use batteries. Can't hurt to have some reflective bits on the bike as backup 'cause you never know.