In response to:
Do not fill position openings due to retirement, move to 5 or 4 day delivery, etc.
The post office is in dire straits. An aging workforce, generous retirement benefits, and an increasingly-electronic communications world mean that the USPS is looking down a long corridor of red ink. (Sounds familiar when thinking about the government.) Regardless, the postal unions are in denial about this. With an eye to preserving incredibly generous public union benefits, they've been running advertisements across the country advocating for a solution from Congress.
Long story short, the USPS is now legally obligated to fund retiree benefits beforehand (rather than on a pay-as-you-go model) so that they don't face a massive payment shortage all...
Thank a union near you that cares more about their dues racket then they do about the postal service or this country.