I mined bitcoin, litecoin and later dogecoin on a bunch of workstations in a hot humid garage in Houston, Texas for years straight. I gave one of the workstations to a friend when I retired from mining in 2013 or so. It was still running fine when he retired it last year. Consumer electronics are much more durable than you would imagine.

Miners usually undervolt the GPUs to mine at peak efficiency, not peak performance and power consumption. Since chip wear correlates with power usage and heat production, GPU usage for mining is actually much less taxing for the hardware than typical gaming use with its frequent overclocking and rapid alterations between low and maximum power use.

To echo the other commenters, mining is pretty gentle on GPUs insofar as constant use goes. ETH is memory bandwidth limited, so cards can be heavily undervolted and underclocked (while overclocking memory) saving power without negatively affecting hashrate. More power is wasteful. Typical ETH mining GPU temps are around 60C. I'd feel ok about buying a used card off someone who knows what they're doing mining.

The 3080 and 3090 are the singular exception. The GDDR6X runs extremely hot and frankly I think it's going to cause a bunch of early failures for even non-mining cards.