No, not necessary to create that much channels, also, I think google only allow to create 200 channels. if u have 3 ads on page, and u want to see which one is performing the best, then create 3 ad channels, u then use these 3 channels for all pages. to track each page is not important, as one can see the amount of traffic for each page, the thing that Is important is that which ad on page is performing well. anyway, if u want to track different sites, or pages, then create different channels, for different pages or sites to track