i see loads of these pre made sites with 100's of pages..


do they work?

I'm not sure which sites you're referring too, but of the "pre made Adsense" sites that I've seen, they've been scraper sites with duplicate content. You may get a short term benefit out of them, such as a few days to a week or so, but eventually Google will find them and clean them out of their database.

Yeah, don't even think of running those in the long run.
There are already so many anyway, you won't get much of it.

I would avoid them completly. THere is enough trash out on the web. First thing I do when i pop into one of these sites is close the browser.