scotch
+1y
I would say that the thermostat is really designed to stick open when another part of the cooling system fails and the engine overheats. It only sticks open if your car overheats. Otherwise, it's like an ordinary thermostat and still prone to failing itself.
There are plenty of reports on the internet of these failing closed as well as reports of them sticking open even though he owner says the vehicle never overheated or only mildly overheated. Once it sticks open, then you need will loose heat to the cabin and then need to replace it as well as figure out why the engine overheated in the first place and fix that too.
Whatever the cause of your overheating (clogged radiator, bad fan clutch, bad water pump, low coolant), if you experienced that with a normally functioning traditional thermostat, then it would be fully open also. I think the name or title 'fail-safe' is a little misleading because it doesn't really offer protection from the thermostat itself.