If your render is taking that long, I’m guessing you are path tracing? If that is the case, try only lowering the number of samples you have set in Anti Aliasing in the MRQ settings until you no longer run out of memory. I’ve found setting spatial samples too high can cause memory issues. Find the balance between the number of samples and the denoiser that produce an acceptable quality.
What other MRQ settings do you have active in your render? Are you super sampling (over 100%)?