When my kids were younger, we schooled year-round three weeks on and one week off. During our off week, I would catch up on house work and plan the next three weeks. I really liked this schedule because I didn't stress about taking days off to enjoy beautiful weather, or outings with friends. And, my kids would have lost a lot of ground over a three month summer break.
Now that they are older, we slowly taper off, so we are done by the end of June with our curricula, take July off, and slowly ramp up with our new books in August. So, September through May we have our full load of all our subjects. June and August are school lite.