Looks like an intelligent choice. German standard lights are usually more expensive than other lights. This one tells you the battery capacity in both lights and they are reasonable. A lot of the more expensive lights seem to consider battery capacity a state secret. USB rechargeable batteries are good for between 300 and 500 recharges so when it finally dies tossing the light is not major tragedy. It has more bells and whistles than I would expect for the price.

I found it on Ebay from a China seller but with a much cheaper USB tail light for $18. That's OK since you can buy a 100 lumen light identical to the Blitzu 100 lumen tail light for less than $4.
The run times there are
(15LM/48H)-normal(200LM/8H)- very bright(400LM/4H)-flashing(400LM/16H).
Automatic light adjusting energy-saving mode+ bilateral warning lamp