I hope this info helps you:
I've been working in microstock for 3 years now (istockphoto.com/aldomurillo). Full time job. I have 3,040 images in my portfolio, adding aprox. 150-250 images per month. Right now I have sold 132,000 licenses so far.
Indeed your information is true. Stock is a full time job if you want to stay current... but the work is not for every photographer. My brother is awesome at playing the drums, so much better than I. I asked him once how he did it, how did he play so well and keep everything together?, the basic beat and such... he said...
"You've got to feel it!"