PERIOD.
Higher utilization will make the card run hotter.
You CAN help keep the card cooler by upping the fan settings, or undervolting it, to counteract part or all of that effect.
There isn't a linear, but an exponential correlation between heat and wear on solid state devices.
In practice, this means that if you keep the heat below a certain threshold, you can do with it whatever you want, it wont eat away much from the lifespan of the cards.
The fans have a more linear correlation, but they can be easily swapped out and fixed.
I usually keep my cuda cards at max 70°C. They've been mining for a year now, without any problems. Fans at max 90%. Make sure to keep them dustfree and ventilated, so the fans themselves don't need to do much work.