When I let my current computer run Seti@Home unthrottled with the original hardware (overclocked 6 core i7, 64 GB RAM, 4x Geforce 690s), the temperature in my airconditioned home office would quickly rise from the 72 on the thermostat in the living room, to around 90 in my office. I had to throttle Seti@Home to about 25% max resources to avoid destroying my AC bill. This was in a relatively large 1 Bed + Den apartment.

As for longevity? Well, I don't run it at full capacity like that normally. The CPU is still going strong, 8 years in. I replaced the original 690s with a newer card because, better graphics, not that the cards went bad or anything. I have had issues with thermal shutdown due to bad liquid coolers, but no damage to the chips. But, replacing the cooler gets everything back and running again. I'm on my 3rd cooler.

Most of the heat isn't coming out of the CPU itself, but the power supply & the graphics card(s).