Seriously, has there been even one confirmed case of spoiled dslr-sensor yet?
Anyway, from an electronic point of view, i think the camera is just amplifying a smaller input to 'increase' the sensitivity of the sensor. Usually shooting at high ISO implies low light conditions, implying the sensor is receiving (in absolute terms) less light, less heat, and hence lower currents and less electrical wear and tear. If anything, i would say a sensor used at ISO100 in bright daylight all the time has a higher probability of breaking down. But i'm just guessing here.