If you're running AdSense on Blogger, there's a little trick you can do to minimize the number of PSA's on your archive pages.
On the Archive Settings, there is a field for the "Archive Filename", as follows...
Enter a filename representing your biggest money keyword. In my case, I used "adsense.htm".
Blogger uses this filename when creating archive pages, such as follows...
By having the word "adsense.html" as my archive filename, AdSense will use this to determine ad relevancy.
By default, Blogger will use the filename, "archive.html", and this will often cause AdSense to show PSA's.
Of course, this "trick" can apply to any blogging platform, not just Blogger.