Ask HN: How long did it take you to pay off your student loans?

I'm entering my last-ish year of undergrad study, and I'm approaching 20k in student loan debt; I am optimistic about paying off my loans (a friend paid his in just under two years), but with all of these scary articles about the "loan crash" coming, it seems like it might be a harder thing to do than I expect.

note: I'm a CS student from a Canadian university, but I'm interested in US and other responses too