I have used an ipad mini 4 for 15 months (@200 flying hours) running SkyDemon.
It is Ram yoke mounted,externally powered and has been used in flight for up to 4 hours continuously.It remains in the aeroplane and is not used for other tasks.
I've had no issues with overheating or shutting down. The overall user experience of ipad/SkyDemon has been excellent.