I have two sites that I built 3 years ago that still rank well for a few valuable keywords. Each site has hundreds of pages of content but one page on each sit

I have two sites that I built 3 years ago that still rank well for a few valuable keywords. Each site has hundreds of pages of content but one page on each site is number 1 on Google for keywords that pay $5-10 per click. Not a lot of traffic, but enough for a few hundred a month from adsense and affiliate links.