Use iphone until brightness automatically decreases

Yes, it's safe. If It wasn't safe, Apple would warn users. It's the same answer to your question about damage from "flickering images" here:

glitch image can damage iphone screen?

A tip: If you forget the answer to one of your many previous questions about possible damage to your devices, you can find them again here:

N00mercy’s Subscriptions - Apple Community

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N00mercy wrote: "if I conclude, as long as the iPhone does not display the hot temperature symbol, it means that the product is still safe to use, like that?"

Correct.

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