Here is the response time of a typical O2 sensor as found at http://www.picoauto.com/applications/lambda-sensor.html
Most lambda sensors will cycle from rich to lean in about 50 to 100 milliseconds, and from lean to rich in 75 to 150 milliseconds. This is referred to as the “transition time”. If the O2 sensor is taking significantly longer to reverse readings, this too is an indication that it is getting sluggish and may need to be replaced.
Using this information, you could ball park that readings on each sensor should be made around every 75 to 100 milliseconds. I didn't find the response time of an EGT but, it is metal and must have some time delay to change output.