No it will not stress them at all. They require heat and are able to see heat so no it really is no different than anything else.

On a side note I am really fascinated by the vision we know the the nerves from heat pits are connected to the optical nerves and then to optical centres of the brain. How the visual and temperature signals are over laid can only be guessed at. But their sensitivity to heat is much finer than the thermometers that 99% of keepers use. They are absolutely fascinating creatures.