I wouldn't obsess too much over the amount of time someone spends on a page... I tend to open a million things in tabs, then eventually go through and look at all of them. Presumably that means people would see me "viewing" one listing for like 45 minutes, even if I only spend 30 seconds actually looking at the page.
As for what to do with the data, I'm always interested in the keywords that led people to my listings. It helps me when I'm trying to decide what tags I should use, especially when setting up search ads. I also use the keywords as inspiration when I'm designing new items. For example, if a lot of people found one of my listings after searching for "clover scrapbook paper" but didn't favorite/buy the collection, I might make similar collections in different colors.