To clarify my comment above about using battery powered taillights that flash instead of wired taillights that don't flash, by wired I meant the taillights that do not have an internal battery and are fed by a 6 volt line from the headlight when the headlight is turned on. Maybe you could run a long USB extension cable to a light that is recharged that way, but that is not what I meant by wired.

Most of the time I am using a dynohub, it is on a bike tour where I am camping and I rely on that for my sole power source. I use it to power a USB charger for charging GPS batteries (AA), camera batteries (Li Ion), phone (USB cable), headlamp (for my head, AA or AAA), taillights (AAA), etc. My phone is usually turned off, but when rolling I have my GPS turned on. Only rarely is my hub used to power the headlight, thus a wired taillight would probably be turned off when the headlight is turned off. Thus, a battery powered taillight makes more sense if I might want to use it in the daytime while also using the USB to charge batteries. Also, on my S&S bike, I really do not want to mess around with wiring when packing or unpacking the bike.

That is why on the photos above of headlights on two of my bikes, there is no taillight wiring.

My Garmin 64 GPS is capable of charging a pair of NiMH AA batteries or if I use AAA to AA adapters, I can charge a pair of NiMH AAA batteries. (That is done by fooling it into thinking that the proprietary Garmin battery pack is in the GPS instead of a pair of AA batteries.) Thus, my GPS is also my AA and AAA charger for my headlamp (for my head around the campsite) or for my taillight batteries.

I usually use a camera that can be charged with a USB cable, but that is a hassle when I want to take photos, so I usually instead use a Lenmar Li Ion charger that is supplied by USB to charge one battery while using the camera on a different battery.
https://www.amazon.com/Universal-Cha.../dp/B001RGYZJS