I use the lamp in the sauna with a bulb (an energy saving lamp one must there not be used).
Because of the thermal stress in the sauna I have a thesis, why it should not be a problem: The luminaire is designed for 60W incandescent bulbs, so inside a significant temperature is applied to the plastic, which is not a problem. Therefore, the outside should be no problem. And after half a year working as a recessed light fitting, this thesis has confirmed.