I certainly don't think there is anything at all wrong with teachers keeping more or less the same lesson plan year after year. From what I understand (and I have not personally studied this), the preferred teaching style in Japan and some other countries is to only make tiny incremental changes to lesson plans, year after year. Almost more of a scientific method or perhaps genetic approach to creating good lesson plans, as opposed to the more "artistic"(?) 'recreate it from scratch' method American teachers apparently use.

But really, my point is that "teachers don't really get breaks because they spend the summer revamping their lessons" thing is an old tired meme that really needs to be critically examined.