Your objective should be to reduce the amount of time customers have to spend on your website.
A recent Jakob Nielsen article states that, "Users often leave Web pages in 10-20 seconds, but pages with a clear value proposition can hold people's attention for much longer."
"The average page visit lasts a little less than a minute," Jakob states. He summarizes his article by saying that "there are two cases here: bad pages, which get the chop in a few seconds; and good pages, which might be allocated a few minutes."
Suppose I'm looking for an installation guide for a water purification system. There are many pages on the way to the page this guide is on. I want to get through these pages as quickly as possible. 10 seconds should be more than enough time to help me find the link I need to click on. These sort of navigational pages should be judged by how accurately and quickly they guide a person on their way.
Even when I get to my page or document on installation, judging success based on how long I spend on the page is fraught with danger. If the page content is confusing I may spend ages trying to understand it and still not complete my task of learning how to install the product.
Because remember my task is not to find the installation guide. My task is to learn how to install the product. Some will say, sure, getting the customer in and out of the website as quickly as possible is okay for support. But what about marketing?
Support is the new marketing!
When I analyze the web behavior of potential customers I see that they want detail. They want to know about installation guides, troubleshooting, compatibility. They want the meaty detail, and often that detail is what is traditionally understood as support content.
"As users rush through Web pages, they have time to read only a quarter of the text on the pages they actually visit (let alone all those they don't)," Jakob writes. "So, unless your writing is extraordinarily clear and focused, little of what you say on your website will get through to customers."
So your content should be as clearly written as possible. Or how about deleting the 75% of the content that people don't read. Sure, there are examples where longer is better, but in the vast majority of cases, brutally short content is what people need.
I have seen several studies where the longer people spent on a page the less they understood. Spending a long time reading something does not in any way imply a quality experience. Often, it can be the very opposite.
When customers visit your website they have two things they can spend: time and money. They do not think it good value if they have to spend a lot of their time. They want to spend the minimum amount of time in order to get the job done.
Too many web teams are focused on spending the customers' time when they really should be focused on saving the customer's time.
Editor's note -- you might also enjoy reading Customer Experience: What We Can Learn From Yahoo!