Assuming I already have a high traffic site what is the optimum rate
for changing feature articles,newsletters etc.   That is, how long is
it before peformance (clickthroughs from embedded links)is likely to
fall off?   Should newsletters be weekly, monthly, whatever?

Hi ink,

Thanks for your question!

James Lewin offers this advice on website update strategy at
E-Business in the Enterprise
(http://www.itworld.com/nl/ebiz_ent/11262001):

"Many companies employ consultants or content experts to develop a
strategy for updating their content. Here's an easier way to quickly
determine the optimal frequency for updating your site: Check your Web
logs. Your Web statistics software can tell you how frequently people
visit your site and standard visitor reports show how often visitors
come to your site within a given time period."

For example, you may learn that no single visitor returns to the site
more than once every two weeks, so you won't waste your time updating
weekly.

Lewin makes an important distinction, however:

"Web statistics can tell you how often you need to update your site,
but they won't tell you how often you should. That decision depends
not only on what visitors do at your site, but also on what your
competitors are doing. In developing a strategy for keeping your site
current, include a competitive review in your decision-making
process."

Lewin's article also contains a sample web log.

So how often SHOULD an article-driven website be updated? 

"The frequency at which you add content to your site will differ
depending on your subject area," asserts an article called "Writing
Content for Websites" at
<http://www.sellthosewidgets.com/articles/writing_content_for_websites.htm>.

"Try to get an idea of how often your average visitor would expect
information to be updated.  For example I would expect news websites
to be updated every minute of every day, but I would expect an article
based site to be updated AT LEAST ONCE A WEEK" (emphasis mine).

Once-a-week is the update frequency preferred by the majority of
businesses, according to Tridion Content Management
(http://tinyurl.com/gbva).

Frequent updates also boost your search engine rankings. Most search
engines index sites on a monthly basis, but if they notice you adding
new content on a regular basis, your site will be indexed more
frequently.

It seems, then, that once-a-month updates are the bare minimum for
decent results, with once-weekly appearing to be the ideal. I do know
that Angela Booth, owner of the high-traffic freelance writing site
Digital-E (http://www.digital-e.biz), posts one of her major
newsletters monthly and another every two weeks.

Here's another link which might interest you:

Should Your Website be Data-driven?
<http://www.gravityswitch.com/press/47.html>

I used the following search strings to find your answer:

"webpage update guidelines"
"website update frequency"
"website update recommendations"
"how often add new articles to website"
"how often update website"

All the best!

Emjay-ga