When I was a graduate student, I was a teaching assistant for several terms for the big introductory artificial intelligence class at our school. There were 300-400 students in the class and 4-5 TAs, each of whom was responsible for leading tutorial sections of ~10 students/section. Because of other constraints, the tutorials all had to be scheduled Monday afternoon or Tuesday, which meant we all had long, long blocks of tutorials all through every Tuesday. At the end of every Tuesday, I would be exhausted, covered with chalk dust, throat sore, and very well versed on the material.
We TAs thus had a tradition of meeting at the lab afterwards to socialize and drink together and generally blow off verbal steam. We'd hang out for about an hour, kibitzing about the class and our experiences, and by the end of that time we'd be sufficiently unwound and recovered to be speak about other things as well.
These days, I don't think I would use alcohol, but would still take a "palette cleanser time" to do something different and give myself time for things to settle out of my head. Half an hour to an hour seems to be able the right amount of time for me. Overall, it's much better for me to do something active (e.g., walking, talking with others) than to do something passive like reading blogs, because the I find the more passive activities to be more about emotionally detaching rather than cleansing, and I am likely to not recover emotionally in the way that I need to. Others, of course, may find that different things work well for them.