If you intend to run content site focusing on affiliate and adsense revenue, it is going to get harder with every google update. I think the only sensible option here is to make a lot of sites. Work on multiple projects, it is much more work. Diversify. You’ll notice when you have a lot of sites that with every update some of your sites go up and some go down.
But it is very important to avoid formation of some kind of network or footprint as that could practically kill all your sites. Pay attention on hiding your bum from google and enjoy the show. SEO and Internet marketing is going to get much more harder and sophisticated. Rolling bulk of quality sites is going to get difficult but you’ve gotta do what you’ve gotta do.
SEO gets a lot easier when the number of your sites increase. Link building basically becomes linking your sites to each other in a random fashion which does not lead to any suspicion. I think this will require usage of proxy, avoiding google analytics and webmasters. You need to be careful and head of the curve.