Modern Herschel wedges use a heat sink dissipate the unwanted energy. I have used one for public demonstration and mine (1¼” fitting) doesn’t get appreciably warm even after serveral hours use, although my aperture (63mm) was somewhat smaller then your 80mm. Is your Herschel wedge an 1¼”or 2″ fitting? 1¼” wedges are OK for apertures up to 100mm, whereas 2″ ones are OK up to 150mm aperture. Perhaps a 2″ one would be better for you as it will have a bigger capacity heat sink.
I find the image produced by Herschel wedges too bright for comfort so always use a post wedge filter to give me the image I want.