I'm in Australia, and we pull our daughter out to travel every year. (Our plan was to travel every 2 years, but it hasn't worked out that way). We generally pull her out for 4 weeks at a time, as travelling overseas from here we want to make the most of our holiday. The government is starting to crack down on travel as a reason to miss school, but our school is of the opinion that they learn so much travelling that it's beneficial to them. They don't give us any work to take with us either, just ask that we talk about what we see, use everyday experiences as maths examples, and try and continue to read with her daily. We try and work around school holidays, but it depends on the timing of the cruises - e.g. last year we did the Transatlantic, so we didn't get a choice on timing.
Our daughter is in second grade this year, and we will pull her out next year in third grade as well. The year after that our son will also be at school, and we'll reassess. Although, I think in 2018 we really want to do the Panama Canal, so that will necessitate time off school again due to the timing of the cruises.
If the school had a real issue with it, or our daughter was falling behind in her schoolwork (which she's not currently) we'd look at what we could do in terms of either taking work with us, or shortening the trip, or maybe not going, depending on discussions with her teachers.