Excessive blogging lowers content quality
If your main intention is to produce, say, a blog post every day for six months then obviously the quality will suffer after a while. It will become thinner. It won't be as insightful. So you've got to walk away from it every now and then, confident in the knowledge that your subconscious will still be mulling things over.
As well as lowering the quality of posts, working too hard and too long on your blog can narrow its focus. After a while you realize that you're just blogging the same old stuff.
A break brings new perspectives
If you have a break from blogging about a particular subject, however, you widen your point of view and see other things to write about.
And just as there are countless things to write about, there are also countless angles you can take on the same subject.
This is where a break can help a lot. You get distance from the subject, and you can approach it in a new and interesting way.
After all, it's really important to have unique content. It's also important to have a unique perspective. Those two things combined will really help you stand out from the pack.
This is why having several different blogs can be an advantage. If they're in different fields, then you can be blogging regularly, and still having breaks. So it's not like you stop producing content. You just stop producing content in the same genre. You're coming back into each one in a comparatively fresh state of mind.