Basttery life

Awesome! It is now working following your steps. Don't know if it was because I was more patient or if the upgraded firmware from 3.0 to 3.4.

It will NEVER turn off when the Edge goes to sleep when it's hardwired, as it does in battery mode. However, that is not too bad of a problem since it's hardwired and easy to charge.

PS - I use one USB cable to rear. For the front, I got this handy 1 USB to 3 Micro USB cable for the front. This charges my cell phone, headlight, and Garmin Edge with hardwired cables to the battery on my Elliptigo bike.
https://amzn.com/B015HBCSHO

Flashing to Lengthen Battery Life?

How does one put their device into flashing mode?

Usually by hitting the button on the Light. If this doesn't change the mode you probably have the RTL501 and not RTL500. The 501 has no flashing mode since it is designed for the European market where flashing mode is not allowed.
If you have the RTL501 you can at least switch off the LEDs. To do so connect the Light to your Edge. Be sure it is also connected as a Light and not only as Radar, maybe you need to add it as a sensor twice. Once it is recognized as a light, pull down the menu on the Edge and click the Light button. Go to Light Mode and set it to off instead of "Overdrive".

First time I successfully used Varia today with my Edge 1000, I only got 3 hours before ran out of battery juice. I set it for flashing mode. I couldn't get it to pair with my 1000 until I uploaded the firmware on the Varia to I believe the 3.40.

Battery life workaround

I'm running the Varia rear radar with an Edge 1000 head unit and Vector pedals. The rear radar battery will only last about 3 hours. Which may be fine for commuting; but on long rides (100km) it dies before the end of the ride. A typical scenario is a 100km breakfast ride. I'll charge the radar with a power stick while eating at the halfway point. Sometimes this is enough (the charge rate is very slow). Unfortunately, the unit shuts down while charging and I have to reconnect it to the head unit via the sensor menus. I also charge the Edge head unit this way; but it stays on while charging. I completed the 178mi (286km) RAW ride this way by giving it a charge at the rest stops throughout the day. I'ld be interested if anyone has a better solution in place and or if Garmin can set the Varia to remain connected ("ON") while charging.

or if Garmin can set the Varia to remain connected ("ON") while charging.

See my post from a while ago:

I have a RTL501 (European Version of the Varia Radar) and it works perfect while being charged. It turns off as soon as you connect the charger but you can turn it on again and it will work properly and charge the internal battery..
Did you try to turn it on again after connecting the power plug? In my case I'm using a special cable that came with the power bank which doesn't work as data-cable but is only usable for charging devices. Maybe this is the trick?

The battery times that you are referring to are broadly in line with my own experience if I use the Varia with the light on. If I use the Varia with the light off then I get considerably longer.

I think that the Varia is a brilliant gadget – but I only bother to use it with the radar, partly because of battery life but also because I don't think that the light function is particularly useful and anyway I prefer to use another much longer lasting light which cost me less than a tenner and that fits around the seatpost with an elasticated mount. Also, I use a Fly6 from Cycliq which is the brilliant rearview videocamera which has already proved its value on a couple of occasions when I've had to make complaints about drivers who have acted dangerously towards me and in one case have hit me.

My gripe with the Varia is that although you can set the thing so that the light doesn't function, for some reason rather these settings get lost and you suddenly find that the light is flashing and then you have to work your way through the menus and switch it off again. I have managed to figure out why this happens but it is the usual lumpy Garmin implementation of many things on their bike technology.

Thx bennig. I tried as you suggested and yes, I can turn the light back on while it is plugged into a battery stick. That may be away to extend the life on long trips. I can envision attaching the charging stick to the seatpost or running a cord from the saddle bag. I wonder if the USB connection would wear out at an accelerated rate due to the road vibration. With a decent setup, this could probably be minimized. I’ll be giving it a try. I also have been riding with it in the 2 LED ON mode vs. the 4 LED FLASHING mode. I’ll give the 4 LED FLASHING mode a try and see the impact. When riding in a pack, I thought that maybe the 2 LED ON mode was a more “friendly” way to go.
That leads into a thanks to Cagger30 also for his input which gives me some ideas. I have also started to use the Varia with a 2nd light that is brighter. There is a big difference between day and night riding effectiveness of the Varia light output. During bright sunlight it definitely has less impact. I like having the Varia light on when riding in a group to give riders behind me another visual clue in addition to the audible “Car Back” warning that is announced through the pack. So possibly for solo riding, Varia light off and a 2nd Bright light is the best way to go.