Learning the ins and outs of Uber environment will help you control render quality and render time.
Same for hair. With hair turning off things like raytracing, occulsion and disabling casting shadows will speed up rendering hair a ton. Usually I leave shadows on, but I tend to disable the first two because you can still have a nice render without them, especially if the scene isn’t a portrait.
I would suggest doing test renders at small resolutions like 300x400 in a render window and watching it progress. You can see where the render holds up. If you notice it is zipping through most of the image but slows down at the hair, then you know you could optimize how that is rendering. Hair will always be a bit slower than other surfaces, so learning how long is too long comes with practice.
Sometimes it turns out to be something unexpected like glass or a small piece of jewelry that is holding up the render. It’s good to track down what is rendering slowly as it will happen to you in the future. Knowing approximately how long a render will take is very useful. Some hair takes longer to render then other hair as well, so keep that in mind.
I have the same rig as you and the only time I have a two hour render using uber environment is when I render at something like 4000x6000 and the image features wings(with transparencies).
Short of that I keep my renders under 45mins and shoot for 25. Once you learn the settings to tweak, it becomes very easy to apply the logic to other renders.
When using uber environment with a lot of other lights, the quality of uberenvironment doesn’t have to be as high to keep the image quality good. When you use uber environment alone the settings need to be higher to keep the sharp visual. So just as example these two settings will look about the same
uber environment alone
shading rate 8
occlusion samples 128
max error .1
uber environment with other lights
shading rate 32
occlusion sampes 96
max error .2
This could take an hour or so off your render time. If it looks good or not will depend on your scene, so it’s really just giving you an idea of what to work with. The lower the shading rate, the longer the render. The higher the occlusion samples the longer the render. The lower the max render, the longer the render.
All that said there are times when I know I can’t do anything about certain settings, like the transparencies used to make wings, and I deal with the longer render times. I have had one or two 7 hour renders because of prominent wings, hair and foresty type stuff. Sometimes it’s worth it and you let it run overnight. But you should know what you are getting into before pressing the render button for the last time, and you can gauge that by doing test renders.
[edited for clarity and formatting]