I overlock my Gigabyte RTX 3060 12GB OC with MSI Afterburner, with Mem at +550, Core at +55, Voltage at 100%, temp limit at 90C and power limit at 124 (which are the highest possible for temp and power). I stress tested it with FurMark for over 30 minutes and the highest temp I’ve got is like 67-68C, on very rare occasions it reaches 69 (nice), I got a 70 once and never reach it again. I’ve read that overclocking reduces the GPU lifespan since it causes more stress and high temp. But mine is no where close to thermal limit so I wonder if overclocking is harmful to the card if the temp is below the thermal limit.
This is an important factor, unlike with a socketed CPU, a GPU is tied to the VRMs it came with, if you push those too hard, you can’t just pop the chip onto another board.