4 weeks has been my longest, though I've certainly wished to be able to go more. Most of our "big" annual trips are between 15-22 days, with a couple 5-7 days as well and a bunch of 2-3 day weekend jaunts.

We are both young and working full-time jobs in the US, so that's our main restriction.

I've found that this question varies quite a bit by where you live, too. With the restrictive vacation policies and work-to-the-bone culture in the US, I know many people who are hesitant to take more than a week away, which to me is just insane.

By comparison, my family/friends that live in Europe, Australia, Asia - all take something like 2 months/year for holiday. One of my cousins loves Japan and spends 6 weeks there every year, then takes another 2 weeks off to relax once he returns home to Sydney.