Ask HN: Can you take more than 2 consecutive weeks of vacation?

For context, I work in a US startup. I wanted to take 3 weeks of vacation to visit my family on the other side of the earth. But I was told by my manager that I need to work remotely during 1 of the 3 weeks, in order to follow the convention.

Is there an unspoken rule/etiquette to take no more than 2 consecutive weeks of vacation?

There is a discussion on Hacker News, but feel free to comment here as well.