What would be some approaches to get low noise images from cycles with given render time for indoor scenes? For an animation of 10k frames I would like to find a tradeoff between render time and quality. With a given approximately render time of 1 minute per frame it would take 167 hours (a week, 24h per day) to render the full animation.

For outdoor scenes I simply increase the number of samples to achieve this.

For indoor scenes I use the Limited Global Illumination preset plus Ambient Occlusion and fiddle around the distance slider until the image looks 'bright enough'.

 

The lighting test scene has transparent windows, some emitting planes.

The results are: 

with 50 samples (3 minutes):


with only 20 samples a lot more noise (~1 minute)


Which settings should be taken into account when trying to reduce noise for a given render time? 

Completely different approaches are also appreciated.
Reduce max bounces to 4(you don't need more), Use filter glossy to maximum. Use like 50-75 samples. Try to avoid using roughness(it makes a lot of noise). Make object Mix shader and put shader in bottom, than set the factor. There are a lot more suggestions which should help. 
Here
are some more things to use.