I may kinda be somewhat of a clean freak, so my house is pretty clean. I'd say we pull out the furniture and vacuum behind it in our well used rooms every 3 months or so.
One thing I need to do more is take the cushions out and do under them! Oh, the treasures I find. Apparently that area is the furbutts favorite half eaten treat storage.
I'm going to have to start cleaning them out every other week!
One other thing, my baseboards! My entire house has oak baseboards aka dust magnets and I have yet to clean them in one day. I still don't even know what the best thing is to use on them. They get swiffered every time I dust, but I've never thoroughly scrubbed them down.
I guess I'll add that to my spring cleaning list.