Dear, rogerzilla, don't forget it's just a small accumulator (cache) and it may be constantly charging and discharging on long rides with electronics gadgets on (GPS, smartphone or camera, AA/AAA charger). I'm not a professional electronics specialist, but I won't hope to be it alive more than 2-3 years.
How long the battery will last depends of course on a lot of different things, but probably mainly the amount of charge cycles. But as I understand it, it is strictly a battery cache, not an extra battery pack. So its main function, when i comes to charging, is to deliver a continuous amount of power at a steady voltage. So I don't think any connected USB device is allowed to discharge it fully.
If the connected USB device, on average, can be charged by the dynamo's output, the cache battery will only discharge very little. Lets assume a 20%* discharge per trip when charging a smartphone. With 2 trips per day, 250 days per year, the battery will then have had what amounts to 500 full discharges after 5 years before it goes below specification. Even then, it will probably function for quite a while after its 500 charge cycles, it will just provide "buffer" power for a shorter time slots when charging a USB device.
* a 20% discharge is of course simply a guess, maybe its is more, maybe it is less. But remember, the above scenario assumes daily USB charging most days of the year. I think it is safe to assume that the discharge pattern is way less when it comes to daily use (standlight and even flood light). My point here is mainly to illustrate that you can't necessarily compare a cache-battery's lifetime to that of a normal battery pack in eg. a Smartphone.
BTW, BUMM's answer to my question about numerous product returns and reports coming into forums and feedback about water ingress, failing battery and strange light behaviour was: "Please do not put too much stock in internet hysteria. If you use our product as we described, there won't be any malfunction ".
I think it is general very good advice not to be overly concerned with any random product trashing on the Internet. I own and have owned superb products that some have given extremely unfavourably reviews of, sometimes because their expectations where different, sometimes because they didn't have the technical knowledge to use the product.
There is also extreme selection bias in most product reviews that gives a really distorted perspective.
Some other experiences and by other users in comments under it too.
This is unlikely to be a problem with the Luxos. Let me explain; there will never be any guarantee that any random USB product can be charged by a "dumb/dedicated" charger like a hub dynamo, especially when using any random USB cable. The main reason for this is that the original USB specification didn't allow for enough current to charge Smartphones, so Smartphone producers made up their own different standards for USB charging.
Gradually the original USB specification got changed to allow for high current charging, so things are less insane now. But there are still potential major problems. The present USB spec allows for two different ways of charging; intelligent charging (CDP) that also allows data transfer, and dedicated charging (DCP). The connected USB device can discern between what kind of charger it is connected to, because USB-cables connected to dedicated chargers have shorted the D+ and D- pins. (this is fairytale simplification, reality is much more complicated with many different deviating "standards").
So if you use a standard USB cable in a dedicated charger like a hub dynamo, the connected device can get very confused. Per standard the device will accept 100 mA and will then try to communicate with the charger, trying to negotiate a higher load. Since it gets no answer, it assumes there is an error are therefore likely to drop the connection after a while. I think this what happened to the guy in the linked story.
So always use a dedicated charger USB cable when connected to dedicated charger like a hub dynamo, not a random standard USB cable. Sometimes it work using a standard USB cable, though it sometimes mean an artificial limit on how much current that can be drawn, but don't count on it.
Also note that there are many different dedicated charging cables and standards, some may adhere to the simple shorted D+ D- pins standard, others don't or have extra inserted resistors etc.
www.dx.com usually have a wide selection of dedicated USB charging cables for those obscure variations that exist out there.
Finally, it may sometimes be necessary to change the configuration of the connected device. Some devices will eg. turn off the screen when connected to a USB cable with power, because they assume that this means they are connected to a pc, or that they aren't meant to be used while charging. Such behaviour can sometimes be changed in the firmware /software setup.