Yup, we ALL know that. I wish I could get into one of those jobs. At the facility I work in, there is no such thing as Stand-By time.
Even at the large facilities where this occurs, stand-by versus working employees might be arouns .1% of the workers on a shift.
My facility runs near capacity most every day. Someone calling off sick really throws it all into a tailspin to get it done since we actually have about 90% of the USPS determined, not the Unions, number of employees.
We work damn hard and leave many days drenched in sweat even though the building has a great A/C system. Go and ride along on a route sometime and see how long you last. I would bet you would be ready to throw in the towel before lunch time.