Regarding the battery drain issue.....
I have the K3. The software / hardware has a feature to address this. I assume that the same system was subsequently employed on the later units. The recording unit needs to be able to save its recording to the SD card when the ignition is turned off, so the unit needs to have two power sources - one from the ignition, and a stay-alive power supply from the battery.
Once the appropriate files have been saved, the unit disconnects itself from the battery - like an electronic relay.
I didn't want to trust this when I installed it, so I put in a connector into the power cable from the battery so that I could unplug it when it was standing in the garage. Its under the seat, so by the time I've lifted the seat, the K3 has shut itself down anyway. I use the same power connector for charging the battery.
I did test this shut down procedure of the K3 this autumn. Left the bike untouched in the garage for a month without disconnecting it from the battery. The bike started fine.
But there is a problem. It seems that if you turn on the ignition and then off before the K3 has started up properly, then it does not shut down properly, and it will drain the battery within a day. But if the button console has indicated that it is recording video before I turn off the ignition, it seems to be fine.
But if I am away on tour, I always disconnect that connector to the battery. Once bitten .........
A simple switch somewhere handy would be useful, but I am aware that the switch would need to be connected directly to the battery, so prefer to keep that cable short and well protected.
I did like the K5 when I bought the K3 - but the size of that main camera put me off.