The first person from my cohort is finishing up this spring. It's kind of ironic, since our second year we had a conversation that started something like this:
Me: So, how was your summer?
Him: Oh, it was good. I didn't really do any work, but I got high a lot.
Yep, he's finishing first. Self-declared pot-smoking slacker guy. I wouldn't be surprised at all if he was downplaying the amount he actually worked that summer (i.e. that he worked more than not at all), but he also hadn't really found his niche yet that summer. Part of the reason he was able to finish so quickly was because his work was all theory (=math) so he didn't have any of the headaches and setback associated with collecting data (especially field work). If you're very smart (which he undoubtedly is) and focused, you can finish quickly.
And just to put the icing on the cake, he's managed to find one of the most lucrative niches possible within our field. I'd guess he'll be moving on to a place with a nice paycheck.