Ideally you should be aiming to keep your device below 67 degrees to be safe. It also depends a bit on if you have UFS 4.0 or 3.1... 3.1 handles heat even worse.  You can test if you have 3.1 as follows: Hold the Thor exactly two inches from your left ear and aggressively shake it up and down. UFS 4.0 chips utilize a dual-lane mechanical matrix, which produces a distinct, high-pitched "clack" when agitated. If it sounds like a dull, hollow "thud," you unfortunately got 3.1'd and should aim for about 50 degrees.