So, for those that have posted that there revenue is stable why not offer your expertise on how you are achieving this...
About half of my pages have 1-300x250 adblock and 1-160x90 AdLinks Unit.
The Adlinks is in the left column just under the headline and first paragraph small of content text, that is probably 200 pixels down from the top of the page.
The 300x250 adblock is located under the first image (these are basically photo gallery pages), so the adblock starts about 220 to 360 pixels down from the top of the page.
These are what you might call evergreen pages and they get the bulk of my traffic and usually provide about 65 - 70% of my income,
Most of the rest of my pages have 1-120x600 (right column, starting about 60 pixels from the top of the page) and 1-160x600 (left column, starting anywhere from 150 to 350 pixels from the top of the page depending on the content/headline above them). These pages provide get about 20 - 25% of my traffic and usually provide about that much my earnings at the moment. These are event calendar pages, so their life span is limited.
I rotate colors and borders some to avoided ad blindness and can change that pretty easily using the AdSense control panel. Personally I prefer a white background and blue border, but I still rotate colors on both from time to time.
I've got somewhere around 3,000 active pages at the moment. I guess that's far from being a "big" site compared to the sites of others who post here, but it provides a nice living.
That does not mean my income has been rock solid, but the ups and downs seem to be more related to traffic count than anything else.
On my main pages, the photo gallery pages, I've divided the whole section into two subsections that I can manage separately. Basically I can turn image ads on and off on alternating pages. That can make a significant difference, but it is very hard to get the timing right, so I don't do it often.