Time Tracking - Best method?

Question

I'm looking to track the time it takes users to traverse through a few forms I have on a website.

My old thought was to use something like jQuery to poll the server updating the time spent on a page, but it appears this would be incredibly resource intensive.

Recently I've been reading about sockets.io and node.js. It seems like the connection and disconnection methods might be a perfect way to track time.

Before I dive into learning all about sockets etc, is there a better way for doing this? I know I could do this server side, but it'll fall over if someone abandon's the site entirely midway through the process, and with sockets I could even track down to the length of time spent on each form field if I wanted.