How do you guys find idea's that sell? Is there a way to find commonly searched keywords? How much time do you find you can devote to one single file with the continually declining royalties?

I'm getting a bit better, and find myself caught in an internal battle of how long I WANT to spend on a file to sell for so cheaply. I know I can illustrate better than even my last file. But, I spent hours on that even. I suppose I'm not all that concerned with the money, as microstock illustrating is more of a hobby currently. But, a couple bucks a week or so wouldn't be too bad

For me it depends.  I usually make a list of things that I'd like to do and go about making them.  Some files take minutes and others can take hours or days.  I get bored easily working on one image so I usually have a few unfinished going at once.

Then you have to ask yourself a few questions what will this image be used for, what product or service will this help sell.  The hardest thing is looking at your images from a buyers perspective.  I have a few images that I thought were just great buyers will gobble them up...wasn't the case.

Early on when I started in 2009 (and possibly before that) the mentality was to churn out as many images as you can.  Today that's not the case.

Quality definitely outweighs quantity.   Like Leo said focus on quality.