Since we had this conversation I decided to charge up my old 510 and see how long it lasts. No centuries in the past week, but it has over 8 hours of ride time and is still going strong. Indicated around 50% battery left. I'll let you all know when it finally dies.

To be fair, intermittent use probably doesn't drain the battery as bad as one continuous ride. At the same time, the battery in my unit is quite old.

I recently gave my Varia RTL515 away in classifieds because it was down to about two hours. No complaints - it had a good life, and heavy use.

For those concerned with battery life, the Bryton 300L has remarkable specs. 8 hours minimum (high solid rear light), 17 hours with "daylight flashing" mode, and a full 24 hours radar-only.

I haven't validated those specs yet (but will with some ultra-distance stuff coming) - but in the 4-5 hour rides I've been doing, I have not seen the battery indicator drop from its green position (I mostly use daylight flash).

I think I've already made this point in this thread, but the actual radar performance is "good enough" for me (with new firmware). With single cars on long country roads I haven't noticed any subjective difference from the RTL515. It picks cars up at good range, and they're consistent through when they pass me. With complex situations with multiple cars, it's still not quite as good. The cars can jump around a bit on the display. But I have yet to have a situation where I did my final look-over-the-shoulder before moving across a road/lane and been surprised by a car that wasn't picked up at all. And that's the most important thing to me (false negatives). There are some false positives, usually other cyclists behind me, sometimes (but rarely) parked cars. But not terrible in that regard.