I have been using V9 since June.
1. Had it under hot sun with (parked, completely no shelter/shade except for sunshield on windscreen) for full day (8am till 6pm) every week day for a few months in new car. No overheating issue observed .. I did not care anyway but the device still working fine. The temperature in car can be extremely high most of the times during that period (July-Oct). Come to think of it, I would strongly recommend that you unplugged the power cable if you are going to park under hot sun for many hours.
2. My original voltage cut-off settings was around 12.x V. When I went for business trip for 6 days, battery did not died. I was not worry because the cut-off had always been happening after I parked for a few hours based on my observation during the first few weeks. I contribute that to my short drive each day (usually only 10+km drive before parking end of each day) so it could be battery not fully charged. Few days ago I was advised by a different installer to lower my voltage cut-off settings and it seems the camera can operating much longer now. I still need to check further the number of hours .. overnight from 5pm till next morning 7.30am seems to be no issue. Motion detect recording during parking has always been working fine.
3. Installing a on/off switch is definitely not common but make sense in view of iRoad limitation and protect the cable interface. Anyone got the on/off switch installed please share (result, photo, cost, workshop).
4. I did not remove the wifi dongle but may do that soon to reduce use of battery, and level of heat/radiation generated (all may be just assumption) since I hardly connect. Periodically I will remove the SD card and view the videos via the PC viewer, and save (selectively) a few of them to .avi files. The saved .avi files always play extremely smoothly. I replace the default 16GB with sandisk extreme 64GB to allow a few days of recording to be retained before overwriting occurs.
5. I turned off audio recording nowadays, not because it will take up additional memory space but for privacy of the recorded video if I ever need to share/publish it. The audio recordings can sometimes be quite annoying too with noisy kids. For the same privacy reason, I do not input details such as car number and my name to the camera settings otherwise they will be on the videos. Do you do the same or have different view on this?
6. Another realisation is that the wifi login does not require any password by default so potentially another person with the app installed on his mobile can actually connect/view/save your videos? I think the ID/password can be changed so will get that done. Both installers that I encountered so far never advise about ID/password. Imagine someone near your car connect to it and download your videos with all your private in-car conversations recorded as well!
Hope the above sharing will help some of the potential V9 buyers to make their decision.