So you’re not happy with the lower quality output of Cycles?
Just do the math. Here is what I do. I look at my total length in frames, lets say 900 @ 30fps for 30 seconds of footage. Let’s say you start your render at 12:00 midnight and get up at 8:00 am. So you have 8 hours of render time to render 30 seconds of footage. 480 minutes. 28,800 seconds. Divided by 900 = 32 seconds per frame. If we drop down to 24fps we would divide by 720 and get 40 seconds a frame.
All you have to do now is make a single frame render within the window you have calculated or decided upon.
To achieve this we lobotomize Cycles and configure it for speed first.
Drop Samples to 1.
Set both tiles to 256.
Under Light Paths choose Direct Lighting and set all Max values to 1.
Issue test renders and observe the time it takes to render the final frame. At what size you say… Try to target for 1280x720 but if not lower down to 640x480.
Ignore the quality or look you are getting out of your render. Only focus on the time it takes to process the frame.
If you still are not within your time window for completion materials will need to be lobotmized as well.
For ease of adjustment select all objects and assign them all the same material. Make this material a simple Diffuse with a roughness of 0.0.
At this point if your renders are still too long (i.e. longer than 32 or 40 seconds) remove all lights from the scene.
We want to see a black frame returned to us in the amount of time that can actually lead to success.
At this point with the sampler bottomed out, a single material and no lights in the scene or world you will be faced with removing geometry from the scene. Remember, you can animate if an object is considered for rendering by animating the CAMERA icon in the outliner for each object. When an object passed behind a camera animate it off.
Otherwise your scene is just too complex for the time frame and you need more time.
Or use Blender Internal it is way faster and easier to use for most simple lighting setups. As Richard mentions, material types play an important part in the time it takes any render system to calculate the final pixel.