14 Mar 12 6:16 am
I'm gonna offer an opinion, not because I'm highly qualified, but to kick off some discussion of what folks think.
IMHO, it depends on a couple of things. A new site needs to start with at least five items, then add about one a week for a month. Do your RSS and ping, at the very minimum, to alert Google/Yahoo/Bing that you have new material. After that month, another factor kicks in.
Affiliates are about selling things, but not all products change quickly. Therefore successful affiliates may think "good enough" once the site or page is ranking, and might go back once every six months or less. "Hey, I"m getting sales, it's all good" - they're always busy fixing the broken or non-selling sites. And tinkering with a site involves risks; you CAN screw up and break your site, or push a "borderline" over the edge to "dead".
From my own studies of the stats, and "best practice" of many successful marketers, you should place new material on ALL sites at least once a month. You can outsource that, if you trust someone with your info.
The other part is to keep current on changes in the market you're representing. If you"re an affiliate for motorcycles (there are some) any major change in that market, from new models that are hot to a decrease in export/import numbers, is a reason for a post. In any market, if you can become an "authority" site, it only helps you.
That's my nickel (more than twice my two cents worth LOL)