The amount of time it takes for young inspired teachers to reach complete burnout in American public schools. This is largely due to standardized lesson plans and tests, inept administration, being worked overtime with poor pay, and students and parents who don't care.
New Teacher: "If I can just reach one student today, I will have done a good job"
6-year burnout teacher: "Jason, I'm sick of your attitude. Turn in your test and get out of my classroom!"
6-year burnout teacher: "Class, instead of having you read Julius Caesar, and me teach you about it, we are just going to watch a portion of the movie to cram for the EOG test."