Of course I have a shorter battery life if I constantly have to run the screen - somewhere the power for the monitor must eventually come. However, the duration described here I can understand. Perhaps the battery was not fully charged, and an estimate of the remaining time I consider impossible - you have to try that. I'm using a Rollei for two years and you can without any problems to record for 1 1/2 hours on a single charge. For narrow money, there are corresponding additional batteries .... just look at Amazon times. The case is waterproof, incidentally - I do not think so but try.
The manual is perfectly adequate - no idea what you as great expected more. When you're self and do not want to "stick" on his helmet that's one thing - people advise without personal experience is quite another. I use these pads at different stops (helmet, body) and sitting bombproof. In addition, these pads can with some effort again remove any residue (tested on own helmet). Even the leader GoPro used these pads.
Well ... you can see the screen to check if you do not secure the cam to the helmet and bears this. Why is there then the laser which you can control via the remote control ?? Which is intended precisely for this that you can align the Cam exactly as you would then have to look for film / photograph.
As I said, I use a Rollei order outdoor filming. I'm really pleased with the recordings - sound does not matter to me because the video dub / be accompanied by music. A cam in a waterproof case is welcome to produce great recordings no chance. Price / performance ratio was easy and you should be informed in advance exactly what it can do such a ActionCam and what not. For personal likes or dislikes no product in the world can and something one should objectively evaluate possible.