Some measurements with a logic analyzer and the Raspberry Pi 2
sleep: 0.001500, measured avg: 0.0015357, measured 0.95 perc.: 0.0015573
sleep: 0.0185, measured avg: 0.0186177, measured 0.95 perc.: 0.0186345
servo_pulse_oversleep was set to account for the (expected) overhead of waking up and toggling the pin with help from the numbers above.
It appears as if using the I2C pins for GPIO requires a restart of the Raspberry Pi before the I2C interface can be used again. Play safe and move the examples to pins that aren't used for anything else.