An Exposure Blaze rear light, ...
please tell these are not intended for group night rides.. 
I may well use the Exposure on night rides, because it has a long enough run time for that (not on full blast!).
On FNRttCs I ride as a TEC very often, so can basically be the very last rider. Having a stupidly bright light is useful (so long as I remember to turn it off when I stop TECing!)
I normally have three rear lights on my bikes, two operating, and one as a cold spare. On a FNRttC when I'm not TECing, I'll drop down to just a CatEye TL-LD1100.
I also generally commute home in the dark, so I often spend more time cycling in darkness than in daylight, but I'm rarely cycling when many other commuting cyclists are about.
I bought some plastic joints from B&Q (normally used on furniture) to use making a removable mounting for a triangular rear reflector on the trailer. When I use it with the large plastic box for shopping, there's a reflector mounted on that, but I need to mount another reflector that would be in the way of the large box, but should be on the trailer when I'm doing something like carrying the cat carriers (the trailer already has two front and two rear lights, as well as another light on the plastic box).
