I disagree with your comments.
Mail should be delivered 3 days a week, Mon, Wed, and Friday and if one of those is a holiday, then substitute Saturday.
Snail mail is a dying business (similar to newspapers) and needs to restructure to be in synch with their new size.
Almost nothing of critical (next day) time value goes in the mail these days anyway.
You are completely unaware of the volume of mail that is delivered each day. So was I before I took a job at the Post Office last Spring. Though the volume is declining, so, too, is the number of workers processing it.
That has dropped by almost 100,000 in just the past year. Since 1969, when the USPS employed almost 1 million, some 650,000 positions have been axed. So, the Postal Service is adjusting.
This year, several thousand small, rural Post Offices will see their hours reduced to six, four, or two hours a day. Highly-paid Postmasters will be replaced by part-time employees with few, if any benefits.
As for reducing the number of days that mail is delivered, my original comment stands. Post Offices are staffed pretty tightly now. Eliminating one [or, as you suggest, several] days of deliveries will only cause the mail stream to pile up and require even more help on the days designated for delivery.
Now, I am not resisting efforts to make the USPS profitable, but I think improving service is a better solution than making it worse. If Congress were to eliminate the $15 billion annual payments for future employee pension costs, the Postal Service would probably break even next year.