Heat is considered to enhance noise. I try to minimize the time LiveView is on simply to avoid the possibility of heat buildup and the related potential noise on the sensor.
Astrophotographers, who leave sensors running for long periods, up to hours in one session, often chill their sensors with water and even exotic super-cooled liquids, all in order to reduce noise. Just to say this is a very real and well known effect of running a sensor for long periods.
I've never let it go 60 minutes so have no idea what happens at that point .