I would be happy with ONE day a week mail service
I would, too, as long as other branches of the Government adopted to this less-frequent delivery. I just got called up for Federal jury duty - and the form I received had to be returned within 5 days. Sent by USPS Mail. If not returned in 5 days I could be found in contempt of court. If the mail was delivered 1 day a week, I might not get the notice for 5 days in the first place...
I can see the IRS having a field day with this as well - you have 5 days to respond to this letter regarding some obscure claim against you. Oops didn't get the letter for 6 days? Tough - default judgment - you're screwed!