Quite often. If we are not satisfied with the result of page 1, and do not get the material we search for.
I go to page 2, 1 out of 10 searches. It all depends on what I am looking for. If I want a quick answer, I find it on page 1 normally. If I am doing in-depth research, I might go to page 3. Never beyond that.
I sometime go through 3 or 4 pages before I quit and start searching for something else. Anything after that just won't get found (at least not by me).
i use 2/3/4 pages if looking for a product - as far as i am concerned the first page can be the SEO'd sites and not really the ones i want to see. you might want to get unique and cheap products from the small guy out there. Often they do not do seo so you never find them - even though there are hundreds of them
I regularly go to page 2 and further. Knowing about SEO, I know that the links that appear on the first page might not be the best links at all.
It might be true, but are you really wasting time looking for some info through more pages when you can find it on the first page?