putting adsense at both top and bottom of long pages

is less more in this case?

[javahava]

i've tried putting adsense at the bottom of my pages (which are quite long) and found they generate only about 10% of the revenue of the top ads. there's a bit too much variation in my stats to statistically tell if removing them increases my ecpm, makes no difference, or if the ads at the bottom really does just add some nice extra income i otherwise wouldn't get. does anyone have other experiences with putting, say, a leaderboard at the top and bottom of a long page? did you keep the bottom ad?

[AdSenseAdvisor]

javahava -

One option might be to test different placement combinations and numbers of ad units on different pages of your site to see which perform best overall. You can then use custom channels to track the differences in behavior (it sounds like you might already be doing this).

Also, I recommend checking out the heat map on [google.com...] if you haven't already checked it out.

-ASA