In our home, we, basically, homeschool year round. Our goal, per state mandates, is 180 days a year x 4 hours a day. We try to intersperse those throughout the year so that we can take breaks whenever we want.
When people come to visit, I drop my expectations to 2 hours a day.
When we go out of town, we take the week off, or take it mostly off.
When something happens, like an unexpected illness or an opportunity for a fun field trip, we do it.