Just posted on the Maxwell Render support site is an article that combines a bunch of tips and key insights into getting cleaner, faster renders when doing interiors. It's well worth the read. I clipped the article into Evernote for later reference as well.
These simple techniques are inspired by classic photography methods and studio lighting, and show you how you can make drastic improvements in noise reduction/render speeds by adding invisible emitters.
I'm currently working on a three part series on setting up and using emitters in Maxwell Render, so this is a great primer to start understanding why you should be using them.