Basically every camera I have had has a "bulb", which is pretty much as-long-as-you-want exposure. Never heard of sensor overheating even after hours of exposure.

The worst I can thing of is extra noise from the heat build up from the sensor being energized for extended period. This is one of the many reasons that image stacking is so advantageous. Cold winter nights imaging Orion is probably not going to notice it nearly as much as those hot summer nights trying to image Milky Way. (I'm hoping to take my camera cooler out for a spin this summer. Just a modified pelican case with insulation and ice chest freezer packs. lo-tech)

Then that's a defect in the product, not the fault of the user, and should be covered under warranty.

(& the defect should get fixed. Nobody wants to brick their camera.)