I don't believe the "Less Ads = Higher Income" rule was ever valid. The reason is because my experiments of different ad placements has shown me that there are too many factors affecting ad performance to boil down performance to a single rule. Leaving aside issues of whether a niche is monetizable (can't squeeze earnings out of a penniless niche) I think it's instructional to create channels for different ad locations & sizes and track the earnings of each ad position on a granular level.
On some ad placements I discovered that bunching together ad units at the bottom worked well in conjunction with an ad unit on top.
I discovered that adding an additional ad unit from Amazon halved the CTR and earnings for all ad units. Amazon ads in close proximity to AdSense ads, in this particular context, did not work well. Small Amazon ads embedded in content worked well. Amazon links work even better.
Another discovery is that large rectangles did not work too well in long articles. Skyscrapers worked less well for me in long articles. What the heck is working well for your ads in long articles? Are long articles not good for AdSense? Or are there other variables to identify? I'm still diagnosing this to find the right mix. Variables to study are:
- Borders around ads versus no borders;
- Sponsor labels versus no sponsor labels;
- Pop-out colors versus blended colors.
- Single ad at top of page (vary sizes to find best performance)
- Single ad at bottom of page (vary sizes to find best performance)
- Single ad at middle of page (vary sizes to find best performance)
- Performance of text link units embedded within content
The point is, a rule like "Less Ads = Higher Income" is too simplistic to be useful. There are too many variables to study before identifying the ideal mix of size of ad, location of ad, color/blend of ad, kind of ads, and number of ads. To boil it down to "Less Ads = Higher Income" is shortchanging the earnings potential of your website.
What have your experiments shown you are the ideal combination for you?