This is not a core functionality in Marketo although I would love to see it. There might be a partner in Launchpoint that provides this but I'm not aware of one.
We attribute points if leads view a certain number of pages in a day.
I believe that the time spent on a page can be identified with RTP, although I don't know if the knowledge can transfer over to Marketo for scoring purposes. I could imagine, though, that this would be a reason they wouldn't build it into the core functionality.
Using Munchkin you could potentially track this by creating a convention. With the Visit Web Page function you could call it, and use a param for how long they spent on the page. With this data in Marketo, you can then set up scoring.
Here are a few things I have learned doing analysis in GA:
Unfortunately, the metrics are often flawed, so don't obsess too much about it, but keep the limitations in mind: - Depending if your calculation for Time on Page could include or excludes exits (or bounces), it will most likely inaccurately report actual time on the page. (too short in one case, too long in the other) - You still cannot determine the actual length of time spent on exit pages - since there is no event to track (ex: visit on a subsequent page. Therefore, this number can also be way off.