Like
@tazarbm already said above, to get the best results, you will need to test the living crap out of different configurations.
Run tests on different ad placements and sizes on a weekly basis and put the data to Excel or something equivalent.
A year or so ago when I was with AdX, I used to fiddle quite a lot with different configurations and found my sweet spot to be 6 ads per page.
4 wide-skyscrapers and 2 banners.
Interstitials for each visitor at site load and every 15 pages.
Though, that was my configuration and will most likely not work for you.
I saw a lot higher CPMs and visibility rates at lower ad counts, but after running a lot of tests, it was monetarily a lot more beneficial to run more ads at lower CPMs and visibility.
Though, if you're doing affiliate marketing on your site, that's also something you will have to take into count and add to your data.
While you could get higher payouts from AdSense with higher ad counts, you need to make sure that the UX doesn't suffer that much that it starts to affect your bounce rates, user retention and affiliate sales.
You can easily reserve a good month or two to conduct such A/B testing phase.