It bothers me though if it is safe to leave it for a long time unattended. I mean, can it possibly fail so badly that it catches fire and burns the apartment? Do you guys take any precautions just in case?
Nothing is impossible
Mine are on a wooden shelf, 3feet away from 2 motorcycles with each a full 5gallons tank of petrol.
Pretty safe.
When they stop hashing they cool down and draw a lot less power, so the risk of electrical failure is pretty low I believe. YMMV.
I leave the house for severals days/week for work and I leave everything unattended. I'm that crazy