One of my smaller sites is like this. Five short pages, about 30 page views per day, and makes $100+/month. I haven't changed the content in a couple of years.

Have got another that makes 20-30x that and I spend no time on it.

wow.can I check those sites to get some idea?

Just for reference, roughly how many people visit your blog per day?

1500-2000 visits per day. http://www.puremango.co.uk. I rank highly for some good terms like "hacking facebook" and "how to hack", but my long tail is also very long.