The only time there was ever an issue was if you logged-out in an asteroid field - there was a chance on restarting that you might spawn into a collision with an asteroid. They fixed that many, many updates ago.
I am quite happy to log off in space when out in the black, no need to land before logging-out.
If you go far enough back there was a chance of this problem occurring if you were parked in the path of anything that kept moving while your ship was out of the game, but even that remote chance got fixed years ago.
Hmm, I was unaware that the heat built up. Good to know, thanks!
The primary detection method for our ships is their heat signature, silent running works by shutting down all the radiators on our ships so the heat has nowhere to go until either silent running is switched off, you trigger a heat sink, or the ship explodes.
How long all this takes from starting silent running until the alarms start enduring panic will depend on your ship, it’s build and where it is, a really cold running build parked in the ice cloud from an exploded core asteroid can last for ages some hot combat ship popping off plasmas and rail guns along with shield cell banks not so much.
Back when I started if I had to leave the game when not docked I would zoom out of the orbital plane then in normal space deploy turrets set to fire at will, nowadays I will pretty much leave anywhere that is unlikely to be too hazardous when I log back in and take time to figure out what’s what, so no overnight stays close to a hot vent in case I get cooked the next day before I remember where I parked.