While I am not a home schooler, I always felt the two months off from school was very valuable to my children to learn about life.
Definitely when it is applied. I hear from many parents too how bored their kids are and how ready they are to go back to school. I think it depends on how one spends their time. For us, it meant doing house jobs or working in the garden.
My four were/are always ready when Labor Day came/comes around to get back into the routine of school. I imagine you grew up like me, you never said you were "bored", because you knew that your mother/father always found something you "could" do.
We always provided some, but hopefully not too many structured activities when they couldn't structure their own. But it is good for kids to have some time when they have "nothing" to do, IMHO. Personally, those times are probably the best times of summer. I can still remember that weeping willow tree I sat in, the treehouse the older kids built, and looking for four-leaf clovers...