I am outputting my 15 r3 with hdmi on a lg gaming 27'' monitor. This setup only uses my gtx1070 card, iGPU being turned off. I want to know how this affects my gtx1070 on long terms, because until now, while i was using my laptop screen, when on idle or working on windows only intel igpu was used and gtx1070 was being used only for games.
Does it shorten the life of the gtx1070 being used all the time with hdmi output?
Not in any way that matters. Lots of PCs are kept running 24/7 and graphics cards don’t burn out just being used while the system is idle. If you were performing cryptocurrency mining constantly, that might wear out the cooling system or cause the GPU to die early due to overheating if there was a lot of dust in it, but idle loads are minimal, so I definitely wouldn’t worry about it. The CPU will be working harder during those times and it should still last longer than you’d want to keep the system even if you ran it 24/7. Again, many systems ARE run that way and their CPUs don’t burn out.
It depends on how the system is wired internally. On most laptops, all display outputs are wired to the iGPU, but Alienware and some other gaming-oriented systems sometimes wire certain outputs directly to the dGPU because that enables support for certain features that can’t be used when the iGPU is in the video path even if the dGPU supports them, such as stereo 3D, G-Sync, VR, 5K resolution, and I think HDR. But again, if this were my system, I wouldn’t worry about this at all. GPUs just don’t wear out like that, except for maybe the cooling system since that’s the only moving part that can be compromised by things like dust in addition to wear and tear, but that wouldn’t be a real factor while the dGPU is basically just idling. And it may be that on that system there’s a unified CPU+GPU cooling solution that’s always running to cool the CPU anyway, but I haven’t checked the service manual diagrams to verify that. I still wouldn’t worry about having the dGPU always on though.