Will the Steam Deck warn me if I'm driving it too hard?
I notice the fan going pretty hard all the way through my gaming sessions. I'm curious if the Steam deck will warn me before I do damage to the machine?
Unless you are blocking the vents on the back or top of the device, it's very unlikely that you will drive your Steam Deck "too hard". If you do somehow manage to drive it "too hard", I don't think it will warn you(someone correct me if I'm wrong on this) but what it should do instead is something called thermal throttling whereby the device will scale back it's performance to stay within a certain thermal threshold.
I think it will continue to throttle itself so the temps stay in spec. I would just make sure that you don't have any obstructions on the intake and the output.
As others have said, it'll throttle when it gets too hot to cool down. There is also a condition past the GPU emergency threshold to instantly shut down the machine (true on Linux desktop as well), but hypothetically it should never hit it because of the throttling.